Fix bug when change a selected upload file in server or url file.

src/js/jflow-wfform.js

@@ -308,6 +308,9 @@ jQuery.validator.addMethod("exclude_required", function(value, element, options)
 		    		} else {
 		    			$("#urlfile_btn_"+tid).hide();
 		    			$("#"+tid).prop('readonly', false);
+		    			if ($("#"+tid).data("data2upload")) {
+		    				$("#"+tid).removeData( "data2upload" );
+		    			}
 		    		}
 		    	});
 		    	$("[id^=urlfile_btn_]").click(function(){