(XCode) How to resolve "Warning: Multiple build commands for output file ..."

Just met a weird warning message in XCode which is "Warning: Multiple build commands for output file ..." after deleting a resource file, and i checked the file does not exist in resource folder any more, finally i found the the file did appear in "targets/app name/copy bundle resources/", than i figure out i accidentally pressed "Delete reference" when i delete the file, and that's why the resource file still exist in the "copy bundle resources" folder