account for sources being None

core/dbt/parser/schemas.py

@@ -111,12 +111,15 @@
 # ===============================================================================
 
 
-def yaml_from_file(source_file: SchemaSourceFile) -> Dict[str, Any]:
+def yaml_from_file(source_file: SchemaSourceFile) -> Optional[Dict[str, Any]]:
     """If loading the yaml fails, raise an exception."""
     try:
         # source_file.contents can sometimes be None
         contents = load_yaml_text(source_file.contents or "", source_file.path)
 
+        if contents is None:
+            return contents
+
         # When loaded_loaded_at_field is defined as None or null, it shows up in
         # the dict but when it is not defined, it does not show up in the dict
         # We need to capture this to be able to override source level settings later.