fix issue with dcat, code cleanup

Author: david-blasby

modules/library/common-index-model/src/main/java/org/fao/geonet/index/model/gn/IndexRecord.java

@@ -210,7 +210,7 @@ public IndexRecord() {
    */
   public List<String> getGeometriesAsJsonString() {
     if (geometries == null || geometries.isEmpty()) {
-      return null;
+      return new ArrayList<>();
     }
     List<String> result = new ArrayList<>();
 

modules/library/common-search/src/main/java/org/fao/geonet/common/search/ElasticSearchProxy.java

@@ -63,7 +63,7 @@ public class ElasticSearchProxy {
    * request.
    * This allows a GeoJSON to still get the underlying gnindex json.
    */
-  public static String ACCEPT_OVERRIDE_ATTRIBUTE = "accepts-override";
+  public static final String ACCEPT_OVERRIDE_ATTRIBUTE = "accepts-override";
   public static final String[] validContentTypes = {
       "application/json", "text/plain", "application/rss+xml"
   };