Avoid $project fields in case of query.annotations is not defined.

Author: WaVEV

django_mongodb/compiler.py

@@ -26,7 +26,8 @@ def execute_sql(
 
         columns = self.get_columns()
         try:
-            query = self.build_query(columns)
+            # Avoid $project fields in case of query.annotations is not defined.
+            query = self.build_query(columns if self.query.annotations else None)
         except EmptyResultSet:
             return iter([]) if result_type == MULTI else None