Merge pull request #360 from ral-facilities/bugfix/500-internal-serve…

…r-error-#359

500 Internal server error when running DG API on its own and sending Investigations request

datagateway_api/src/common/filter_order_handler.py

@@ -53,8 +53,10 @@ def apply_filters(self, query):
             # Using `type()` because we only want the Python ICAT version, don't want
             # the code to catch objects that inherit from the class e.g.
             # `SearchAPIIncludeFilter`
-            if type(query_filter) is PythonICATIncludeFilter and isinstance(
-                query, SearchAPIQuery,
+            if (
+                Config.config.search_api
+                and type(query_filter) is PythonICATIncludeFilter
+                and isinstance(query, SearchAPIQuery)
             ):
                 query = query.icat_query.query
             query_filter.apply_filter(query)