check the return code of wxStream::Read() in wxImageHandler::DoCanRead()

and avoid reading uninitialized memory when it fails


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@15601 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/image.cpp

@@ -1015,7 +1015,7 @@ int wxImage::GetImageCount( const wxString &name, long type )
 
 bool wxImage::CanRead( wxInputStream &stream )
 {
-    wxList &list=GetHandlers();
+    const wxList& list = GetHandlers();
 
     for ( wxList::Node *node = list.GetFirst(); node; node = node->GetNext() )
     {