Fix false warning on DELETE endpoints: "Can't set request-id because headers not set"

The check `if not header_param:` incorrectly treats an empty dict {} as
falsy, skipping X-Request-Id injection for every endpoint whose OpenAPI
spec has empty accept and content_type headers. This affects all DELETE
endpoints (delete_detector, delete_priming_group, delete_rule,
reset_detector) and edge_report_metrics_create.

The fix changes the guard to `if header_param is None:` so that an empty
dict correctly falls through to the elif branch and gets the request-id
header set.

Author: brandon-wada

src/groundlight/internalapi.py

@@ -176,7 +176,7 @@ def call_api(self, *args, **kwargs):
         # Note we don't look for header_param in kwargs here, because this method is only called in one place
         # in the generated code, so we can afford to make this brittle.
         header_param = args[4]  # that's the number in the list
-        if not header_param:
+        if header_param is None:
             # This will never happen in normal usage.
             logger.warning("Can't set request-id because headers not set")
         elif not header_param.get(self.REQUEST_ID_HEADER, None):