warning message improved

CHANGELOG

 minerva (15.0.0~alpha.0) stable; urgency=medium
   * Small improvement: when downloading a map results in too big file (>1MB)
     the content is compressed and returned as a zip file (#348)
+  * Small improvement: confirmation dialog when removing "general view"
+    overlays contain proper warning  (#809)
   * Bug fix: position of structural state is preserved on upload CellDesigner 
     file (#671)
 

frontend-js/src/main/js/gui/admin/EditProjectDialog.js

@@ -506,8 +506,14 @@ EditProjectDialog.prototype._createOverlayTable = function () {
     var button = this;
     var overlayId = parseInt($(button).attr("data"));
     var overlay = self._overlayById[overlayId];
+    var confirmationMessage = "Do you want to delete overlay: " + overlay.getName() + "?";
+    if (!overlay.getInputDataAvailable()) {
+      confirmationMessage += "<br/><span style='color:red;font-weight:bold'>Warning: This contains one of the map's " +
+        "diagrams and is required<br/>" +
+        "for map display. Removing it cannot be undone.</span>"
+    }
     return GuiConnector.showConfirmationDialog({
-      message: "Do you want to delete overlay: " + overlay.getName() + "?"
+      message: confirmationMessage
     }).then(function (confirmation) {
       if (confirmation) {
         $(button).attr("disabled", true);