Metadata editor / Fix javascript error in the add thumbnail option wh…

…en the metadata has 1 WMS layer:

Error: [orderBy:notarray] http://errors.angularjs.org/1.8.2/orderBy/notarray\?p0\=%7B%22resource%22%3A%7B%22ref%22%3A%22172%22%2C%22refParent%22%3A%22171%22%2C%22name%22%3A%222%22%2C%22url%22%3A%22https%3A%2F%2Fmaps-cartes.ec.gc.ca%2Farcgis%2Fservices%2FDMS%2FStressCumulatifLittorales%2FMapServer%2FWMSServer%3Frequest%3DGetCapabilities%26service%3DWMS%22%2C%22title%22%3A%22Metadata%20WMS%20layer%22%2C%22abstract%22%3A%22The%20ISO19115%20metadata%20standard%20is%20the%20preferred%20metadata%20standard%20to%20use.%20If%20unsure%20what%20templates%20to%20start%20with%2C%20use%20this%20one.%22%2C%22protocol%22%3A%22OGC%3AWMS%22%7D%7D
    at lib.js?v=65b94734a63ca8491dba95d7439baf1be02c2450:21:168

web-ui/src/main/resources/catalog/components/edit/onlinesrc/OnlineSrcDirective.js

@@ -680,7 +680,13 @@
                 //   });
                 // }
                 // Add each WMS layer to the map
-                scope.layers = scope.gnCurrentEdit.layerConfig;
+                if (scope.gnCurrentEdit.layerConfig == undefined) {
+                  scope.layers = scope.gnCurrentEdit.layerConfig;
+                } else {
+                  scope.layers = Array.isArray(scope.gnCurrentEdit.layerConfig)
+                    ? scope.gnCurrentEdit.layerConfig
+                    : [scope.gnCurrentEdit.layerConfig];
+                }
                 angular.forEach(scope.gnCurrentEdit.layerConfig, function (layer) {
                   scope.map.addLayer(
                     new ol.layer.Tile({