Fix TypeError in by_name() when name is not found

When using `match="equals"` (the default), `by_name()` would return
`None` from `dict.get(name, None)` if the name wasn't found in the
lookup cache. This caused `len(matches)` on line 51 to raise:

    TypeError: object of type 'NoneType' has no len()

This fix changes the default value from `None` to `[]` (empty list),
making it consistent with the `match="contains"` branch which already
initializes `matches = []`.

Author: ree-gupta

pipeline/src/additional_methods/by_name.py.txt

@@ -38,7 +38,7 @@
                     else:
                         cls._instance_lookup[key] = [instance]
         if match == "equals":
-            matches = cls._instance_lookup.get(name, None)
+            matches = cls._instance_lookup.get(name, [])
         elif match == "contains":
             matches = []
             for key, instances in cls._instance_lookup.items():