cid#1660547 avoid Division or modulo by float zero warning

and

cid#1659880 Division or modulo by float zero

drop the default arguments, they are always explicitly set
except for one single case.

Change-Id: I1fce4e7f6ff5c9421c40628e0b6a1e291650e51c
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/189862
Reviewed-by: Caolán McNamara <caolan.mcnamara@collabora.com>
Tested-by: Jenkins

slideshow/source/engine/animationfactory.cxx

@@ -304,8 +304,9 @@ namespace slideshow::internal
                     ENSURE_OR_RETURN_FALSE( mpAttrLayer && mpShape,
                                        "PathAnimation::operator(): Invalid ShapeAttributeLayer" );
 
-                    ::basegfx::B2DPoint rOutPos = ::basegfx::utils::getPositionRelative( maPathPoly,
-                                                                                         nValue );
+                    ::basegfx::B2DPoint rOutPos = ::basegfx::utils::getPositionRelative(maPathPoly,
+                                                                                        nValue,
+                                                                                        basegfx::utils::getLength(maPathPoly));
 
                     // TODO(F1): Determine whether the path is
                     // absolute, or shape-relative.