Bustage fix for change set 9f0e541d6656.

widget/src/windows/nsWindow.cpp

@@ -5013,7 +5013,7 @@ PRBool nsWindow::OnMouseWheel(UINT msg, WPARAM wParam, LPARAM lParam, PRBool& ge
   }
 
   if (!scrollEvent.delta)
-    break;
+    return PR_FALSE; // break
 
   scrollEvent.isShift   = IS_VK_DOWN(NS_VK_SHIFT);
   scrollEvent.isControl = IS_VK_DOWN(NS_VK_CONTROL);