Avoid -Werror=maybe-uninitialized

...as seen at least with --disable-optimized against recent GCC 16 trunk,

> In file included from workdir/UnoApiHeadersTarget/udkapi/comprehensive/com/sun/star/lang/XTypeProvider.hpp:11,
>                  from include/cppuhelper/implbase.hxx:28,
>                  from cppuhelper/source/component_context.cxx:30:
> include/com/sun/star/uno/Sequence.hxx: In constructor ‘com::sun::star::uno::Sequence< <template-parameter-1-1> >::Sequence(sal_Int32) [with E = rtl::OUString]’:
> include/com/sun/star/uno/Sequence.hxx:97:55: error: ‘<unknown>’ may be used uninitialized [-Werror=maybe-uninitialized]
>    97 |     const Type & rType = ::cppu::getTypeFavourUnsigned( this );
>       |                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
> include/com/sun/star/uno/Sequence.hxx:326:1: note: by argument 1 of type ‘const com::sun::star::uno::Sequence<rtl::OUString>*’ to ‘const com::sun::star::uno::Type& cppu::getTypeFavourUnsigned(const com::sun::star::uno::Sequence<T>*) [with T = rtl::OUString]’ declared here
>   326 | getTypeFavourUnsigned(
>       | ^~~~~~~~~~~~~~~~~~~~~
> include/com/sun/star/uno/Sequence.hxx: In constructor ‘com::sun::star::uno::Sequence< <template-parameter-1-1> >::Sequence() [with E = com::sun::star::uno::Any]’:
> include/com/sun/star/uno/Sequence.hxx:60:55: error: ‘<unknown>’ may be used uninitialized [-Werror=maybe-uninitialized]
>    60 |     const Type & rType = ::cppu::getTypeFavourUnsigned( this );
>       |                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
> include/com/sun/star/uno/Sequence.hxx:326:1: note: by argument 1 of type ‘const com::sun::star::uno::Sequence<com::sun::star::uno::Any>*’ to ‘const com::sun::star::uno::Type& cppu::getTypeFavourUnsigned(const com::sun::star::uno::Sequence<T>*) [with T = com::sun::star::uno::Any]’ declared here
>   326 | getTypeFavourUnsigned(
>       | ^~~~~~~~~~~~~~~~~~~~~
> include/com/sun/star/uno/Sequence.hxx: In constructor ‘com::sun::star::uno::Sequence< <template-parameter-1-1> >::Sequence() [with E = signed char]’:
> include/com/sun/star/uno/Sequence.hxx:60:55: error: ‘<unknown>’ may be used uninitialized [-Werror=maybe-uninitialized]
>    60 |     const Type & rType = ::cppu::getTypeFavourUnsigned( this );
>       |                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
> include/com/sun/star/uno/Sequence.hxx:326:1: note: by argument 1 of type ‘const com::sun::star::uno::Sequence<signed char>*’ to ‘const com::sun::star::uno::Type& cppu::getTypeFavourUnsigned(const com::sun::star::uno::Sequence<T>*) [with T = signed char]’ declared here
>   326 | getTypeFavourUnsigned(
>       | ^~~~~~~~~~~~~~~~~~~~~

Change-Id: I700c8a9f2116ff9f017d50b161794bfe06e74e1a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/193057
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergmann@collabora.com>

include/com/sun/star/uno/Sequence.hxx

@@ -57,7 +57,7 @@ typelib_TypeDescriptionReference * Sequence< E >::s_pType = NULL;
 template< class E >
 inline Sequence< E >::Sequence()
 {
-    const Type & rType = ::cppu::getTypeFavourUnsigned( this );
+    const Type & rType = ::cppu::getTypeFavourUnsigned( static_cast<Sequence const *>(NULL) );
     ::uno_type_sequence_construct(
         &_pSequence, rType.getTypeLibType(),
         NULL, 0, cpp_acquire );
@@ -81,7 +81,7 @@ inline Sequence< E >::Sequence(
 template< class E >
 inline Sequence< E >::Sequence( const E * pElements, sal_Int32 len )
 {
-    const Type & rType = ::cppu::getTypeFavourUnsigned( this );
+    const Type & rType = ::cppu::getTypeFavourUnsigned( static_cast<Sequence const *>(NULL) );
 
     bool success =
     ::uno_type_sequence_construct(
@@ -94,7 +94,7 @@ inline Sequence< E >::Sequence( const E * pElements, sal_Int32 len )
 template< class E >
 inline Sequence< E >::Sequence( sal_Int32 len )
 {
-    const Type & rType = ::cppu::getTypeFavourUnsigned( this );
+    const Type & rType = ::cppu::getTypeFavourUnsigned( static_cast<Sequence const *>(NULL) );
     bool success =
     ::uno_type_sequence_construct(
         &_pSequence, rType.getTypeLibType(),
@@ -106,7 +106,7 @@ inline Sequence< E >::Sequence( sal_Int32 len )
 #if defined LIBO_INTERNAL_ONLY
 template<typename E> Sequence<E>::Sequence(std::initializer_list<E> init) {
     if (!uno_type_sequence_construct(
-            &_pSequence, cppu::getTypeFavourUnsigned(this).getTypeLibType(),
+            &_pSequence, cppu::getTypeFavourUnsigned(static_cast<Sequence const *>(NULL)).getTypeLibType(),
             const_cast<E *>(init.begin()), init.size(), cpp_acquire))
     {
         throw std::bad_alloc();
@@ -119,7 +119,7 @@ inline Sequence< E >::~Sequence()
 {
     if (osl_atomic_decrement( &_pSequence->nRefCount ) == 0)
     {
-        const Type & rType = ::cppu::getTypeFavourUnsigned( this );
+        const Type & rType = ::cppu::getTypeFavourUnsigned( static_cast<Sequence const *>(NULL) );
         uno_type_sequence_destroy(
             _pSequence, rType.getTypeLibType(), cpp_release );
     }
@@ -128,7 +128,7 @@ inline Sequence< E >::~Sequence()
 template< class E >
 inline Sequence< E > & Sequence< E >::operator = ( const Sequence & rSeq )
 {
-    const Type & rType = ::cppu::getTypeFavourUnsigned( this );
+    const Type & rType = ::cppu::getTypeFavourUnsigned( static_cast<Sequence const *>(NULL) );
     ::uno_type_sequence_assign(
         &_pSequence, rSeq._pSequence, rType.getTypeLibType(), cpp_release );
     return *this;
@@ -148,7 +148,7 @@ inline bool Sequence< E >::operator == ( const Sequence & rSeq ) const
         return true;
     if (_pSequence->nElements != rSeq._pSequence->nElements)
         return false;
-    const Type & rType = ::cppu::getTypeFavourUnsigned( this );
+    const Type & rType = ::cppu::getTypeFavourUnsigned( static_cast<Sequence const *>(NULL) );
     return ::uno_type_equalData(
         const_cast< Sequence * >( this ), rType.getTypeLibType(),
         const_cast< Sequence * >( &rSeq ), rType.getTypeLibType(),
@@ -165,7 +165,7 @@ inline bool Sequence< E >::operator != ( const Sequence & rSeq ) const
 template< class E >
 inline E * Sequence< E >::getArray()
 {
-    const Type & rType = ::cppu::getTypeFavourUnsigned( this );
+    const Type & rType = ::cppu::getTypeFavourUnsigned( static_cast<Sequence const *>(NULL) );
     bool success =
     ::uno_type_sequence_reference2One(
         &_pSequence, rType.getTypeLibType(),
@@ -210,7 +210,7 @@ inline const E & Sequence< E >::operator [] ( sal_Int32 nIndex ) const
 template< class E >
 inline void Sequence< E >::realloc( sal_Int32 nSize )
 {
-    const Type & rType = ::cppu::getTypeFavourUnsigned( this );
+    const Type & rType = ::cppu::getTypeFavourUnsigned( static_cast<Sequence const *>(NULL) );
     bool success =
     ::uno_type_sequence_realloc(
         &_pSequence, rType.getTypeLibType(), nSize,