wina11y: Return E_INVALIDARG if out param is null

Change-Id: Ia7abdd7fe1fbc5b1a6eaecf7d842852bc3815e6e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/167201
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Tested-by: Jenkins

winaccessibility/source/UAccCOM/AccActionBase.cxx

@@ -58,16 +58,18 @@ COM_DECLSPEC_NOTHROW STDMETHODIMP CAccActionBase::nActions(/*[out,retval]*/long*
 {
     SolarMutexGuard g;
 
+    if (!nActions)
+        return E_INVALIDARG;
+
     try {
 
-    if( pRXAct.is() && nActions != nullptr )
+    if (pRXAct.is())
     {
         *nActions = pRXAct->getAccessibleActionCount();
         return S_OK;
     }
-    if( nActions != nullptr )
-        *nActions = 0;
 
+    *nActions = 0;
     return S_OK;
 
     } catch(...) { return E_FAIL; }