In the assignment operator, watch out if the passed message is ourself.

Fixes a crash in WonderBrush when dragging images over the layer list
to import them and triggering auto-scrolling. WonderBrush caches the
drag message and appearantly calls it's own MouseMoved() hood with the
cached message from within the auto-scrolling code.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29464 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kits/app/Message.cpp

@@ -164,6 +164,9 @@ BMessage::operator=(const BMessage &other)
 {
 	DEBUG_FUNCTION_ENTER;
 
+    if (this == &other)
+        return *this;
+
 	_Clear();
 
 	fHeader = (message_header *)malloc(sizeof(message_header));