Correct the size of bitmap returned by wxRegion::ConvertToBitmap().

The bitmap was 1 pixel smaller than needed due to the unwarranted use of
wxRect::GetRight() and GetBottom() instead of GetWidth() and GetHeight().

Closes #12213.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64874 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/rgncmn.cpp

@@ -60,7 +60,7 @@ bool wxRegionBase::IsEqual(const wxRegion& region) const
 wxBitmap wxRegionBase::ConvertToBitmap() const
 {
     wxRect box = GetBox();
-    wxBitmap bmp(box.GetRight(), box.GetBottom());
+    wxBitmap bmp(box.GetWidth(), box.GetHeight());
     wxMemoryDC dc;
     dc.SelectObject(bmp);
     dc.SetBackground(*wxBLACK_BRUSH);