operator should be reversed -- overlay is background when there is no source available

frontend-js/src/main/js/map/AbstractCustomMap.js

@@ -114,7 +114,7 @@ AbstractCustomMap.prototype.createMapOptions = function () {
   var backgroundOverlays = [];
   for (var i = 0; i < overlays.length; i++) {
     var overlay = overlays[i];
-    if (overlay.getInputDataAvailable()) {
+    if (!overlay.getInputDataAvailable()) {
       backgroundOverlays.push({
         directory: "../map_images/" + self.getProject().getDirectory() + "/" + overlay.getImagesDirectory(self.getId()),
         id: overlay.getId(),