when there is no background show proper error message

CHANGELOG

@@ -16,6 +16,8 @@ minerva (14.0.8) stable; urgency=medium
   * Bug fix: upload from zip file allowed empty overlay name (#1065)
   * Bug fix: genome browser slider didn't work properly in Safari on
     non-default Browser zoom level (#1048)
+  * Bug fix: project without background overlay but with some custom data
+    overlays crashed with an error (#1066)
 
  -- Piotr Gawron <piotr.gawron@uni.lu>  Thu, 23 Jan 2020 12:00:00 +0200
 

frontend-js/src/main/js/gui/leftPanel/OverlayPanel.js

@@ -496,6 +496,9 @@ OverlayPanel.prototype.refresh = function (showDefault) {
       if (overlaysFromServer.length === 0) {
         return Promise.reject(new ValidationError("Project doesn't have a background defined. Please re-upload map in admin panel."));
       }
+      if (self.getMap().getBackgroundDataOverlay() == null) {
+        return Promise.reject(new ValidationError("Project doesn't have a background defined. Please re-upload map in admin panel."));
+      }
       var id = self.getMap().getBackgroundDataOverlay().getId();
       selectedOverlay[id] = true;
     }