fix(flagd): RPC Object resolver tolerates missing value field

MessageToDict drops the value field entirely for DISABLED responses (no value is sent). Fall back to the caller's default_value via .get() instead of raising KeyError; the substitution branch then surfaces the default with reason=DISABLED.

Signed-off-by: Todd Baert <todd.baert@dynatrace.com>

Author: toddbaert

providers/openfeature-provider-flagd/src/openfeature/contrib/provider/flagd/resolvers/grpc.py

@@ -409,9 +409,11 @@ def _resolve(  # noqa: PLR0915 C901
                     flag_key=flag_key, context=context
                 )
                 response = self.stub.ResolveObject(request, **call_args)
-                value = MessageToDict(response, preserving_proto_field_name=True)[
-                    "value"
-                ]
+                # DISABLED responses omit the value field entirely; fall back to default_value
+                # here so the substitution below (or the caller) gets a sane mapping.
+                value = MessageToDict(response, preserving_proto_field_name=True).get(
+                    "value", default_value
+                )
             elif flag_type == FlagType.FLOAT:
                 request = evaluation_pb2.ResolveFloatRequest(
                     flag_key=flag_key, context=context