Added an error message for when child mapping is not properly configured (incorrect type)

Author: bleskes

src/main/java/org/elasticsearch/index/query/HasChildFilterParser.java

@@ -134,6 +134,10 @@ public Filter parse(QueryParseContext parseContext) throws IOException, QueryPar
         }
 
         DocumentMapper parentDocMapper = parseContext.mapperService().documentMapper(parentType);
+        if (parentDocMapper == null) {
+            throw new QueryParsingException(parseContext.index(), "[has_child]  Type [" + childType + "] points to a non existent parent type [" + parentType + "]");
+        }
+
         Filter parentFilter = parseContext.cacheFilter(parentDocMapper.typeFilter(), null);
         HasChildFilter childFilter = new HasChildFilter(query, parentType, childType, parentFilter, searchContext);
         searchContext.addRewrite(childFilter);

src/main/java/org/elasticsearch/index/query/HasChildQueryParser.java

@@ -122,6 +122,10 @@ public Query parse(QueryParseContext parseContext) throws IOException, QueryPars
         String parentType = childDocMapper.parentFieldMapper().type();
         DocumentMapper parentDocMapper = parseContext.mapperService().documentMapper(parentType);
 
+        if (parentDocMapper == null) {
+            throw new QueryParsingException(parseContext.index(), "[has_child]  Type [" + childType + "] points to a non existent parent type [" + parentType + "]");
+        }
+
         // wrap the query with type query
         SearchContext searchContext = SearchContext.current();
         if (searchContext == null) {