[fix] Fixed unsaved changes alert on device page

Author: pandafy

openwisp_controller/config/static/config/js/relevant_templates.js

@@ -73,7 +73,14 @@ django.jQuery(function ($) {
       var value = templates.join(","),
         templateField = templatesFieldName();
       $(`input[name="${templateField}"]`).attr("value", value);
-      if (pageLoading) {
+      if (
+        pageLoading ||
+        // Handle cases where the AJAX request finishes after initial page load.
+        // If we're editing an existing object and the initial value hasn't been set,
+        // assign it now to avoid false positives in the unsaved changes warning.
+        (!isAddingNewObject() &&
+          django._owcInitialValues[templateField] === undefined)
+      ) {
         django._owcInitialValues[templateField] = value;
       }
       $("input.sortedm2m:first").trigger("change");