Fix #140376: Modeling: Better message for showing mesh data transfer

Previously in 308292b5d7 an error message
was added to notify that some selected objects are not valid for mesh
data transfer, that message didn't take account that src==dst is also a
case where the transfer is skipped, that doesn't mean the object is
invalid. So update the logic for this.

Pull Request: https://projects.blender.org/blender/blender/pulls/140463

source/blender/editors/object/object_data_transfer.cc

@@ -530,7 +530,11 @@ static wmOperatorStatus data_transfer_exec(bContext *C, wmOperator *op)
       }
     }
     else {
-      invalid_count++;
+      /* Selected objects contains the active object, in this case `ob_src` is the same as
+       * `ob_dst`, so we don't treat this case as invaid. */
+      if (ob_src != ob_dst) {
+        invalid_count++;
+      }
     }
 
     if (reverse_transfer) {