Fix empty fprime-gds.yml options error (#258)

* Fix empty fprime-gds.yml options error

* readability

Author: thomas-bc

src/fprime_gds/executables/cli.py

@@ -374,6 +374,8 @@ def parse_args(
     def flatten_options(configured_options):
         """Flatten options down to arguments"""
         flattened = []
+        if configured_options is None:
+            return flattened
         for option, value in configured_options.items():
             flattened.append(f"--{option}")
             if value is not None: