Config loading: don't choke on falsy OPENEO_BACKEND_CONFIG

e.g.: also use default when OPENEO_BACKEND_CONFIG is emtpy string

Author: soxofaan

openeo_driver/_version.py

@@ -1 +1 @@
-__version__ = "0.58.1a1"
+__version__ = "0.58.2a1"

openeo_driver/config/load.py

@@ -85,7 +85,7 @@ def _default_config(self) -> ContextManager[Path]:
     def _load(self) -> OpenEoBackendConfig:
         """Load the config from config file."""
         with self._default_config() as default_config:
-            config_path = os.environ.get(self.OPENEO_BACKEND_CONFIG, default_config)
+            config_path = os.environ.get(self.OPENEO_BACKEND_CONFIG) or default_config
             config = load_from_py_file(path=config_path, variable="config", expected_class=self.expected_class)
         if hasattr(config, "id"):
             _log.debug(f"Loaded config {config.id=}")