When a configuration file exists but is empty, YAML parser returns None.
This change returns an empty dict to represent the empty configuration.
This fixes the following issue for empty config file:
File "/home/dereckson/dev/python/general/lib64/python3.13/site-packages/mergedictionaries/app/app.py", line 118, in <lambda> self.context["config"].get("git", []), self.context["git"] ^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'get'