Don't attempt to parse empty datasource

Author: manisandro

src/config_generator/qgs_reader.py

@@ -780,6 +780,9 @@ def __generate_edit_form(self, project, qgs_dir, map_prefix, shortnames, maplaye
     def __parse_datasource(self, datasource):
         """ Parse a QGS datasource URI string. """
 
+        if not datasource:
+            return {}
+
         result = {}
 
         # sql= is placed at end of datasource string, and can contain spaces even if it is not quoted (hurray)