Canvas::path: early return for descendant changes

The ‘rect’ attributes of Path were before the early-return when the
change is for a descendant node.

simgear/canvas/elements/CanvasPath.cxx

@@ -863,6 +863,9 @@ namespace canvas
   //----------------------------------------------------------------------------
   void Path::childChanged(SGPropertyNode* child)
   {
+    if( child->getParent() != _node )
+      return;
+      
     const std::string& name = child->getNameString();
     const std::string &prName = child->getParent()->getNameString();
 
@@ -892,9 +895,6 @@ namespace canvas
       return;
     }
 
-    if( child->getParent() != _node )
-      return;
-
     if( name == "cmd" )
       _attributes_dirty |= CMDS;
     else if( name == "coord" )