Changed behavior of FieldFilter to throw InvalidPathException instead of returning null when a field is queried for on a json array

json-path/src/main/java/com/jayway/jsonpath/internal/filter/FieldFilter.java

@@ -35,7 +35,7 @@ public class FieldFilter extends PathTokenFilter {
     public Object filter(Object obj, JsonProvider jsonProvider, LinkedList<Filter> filters, boolean inArrayContext) {
         if (jsonProvider.isList(obj)) {
             if (!inArrayContext) {
-                return null;
+                throw new InvalidPathException("Trying to access field on array");
             } else {
                 List<Object> result = jsonProvider.createList();
                 for (Object current : jsonProvider.toList(obj)) {