Ensure we don't modify a shared object in wxOSX wxRegion::DoOffset().

Call AllocExclusive() before modifying the object.

Closes #13338.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68279 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/carbon/region.cpp

@@ -191,6 +191,8 @@ bool wxRegion::DoOffset(wxCoord x, wxCoord y)
         // nothing to do
         return true;
 
+    AllocExclusive();
+
     verify_noerr( HIShapeOffset( M_REGION , x , y ) ) ;
 
     return true ;