qapi/introspect.py: set _gen_tree's default ifcond argument to ()

We don't need to create an empty, mutable list to pass to _gen_tree;
since it is now typed as a Sequence, we can use the empty tuple as a
default and omit the argument.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20210216021809.134886-19-jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

scripts/qapi/introspect.py

@@ -254,7 +254,7 @@ def _gen_features(features: Sequence[QAPISchemaFeature]
         return [Annotated(f.name, f.ifcond) for f in features]
 
     def _gen_tree(self, name: str, mtype: str, obj: Dict[str, object],
-                  ifcond: Sequence[str],
+                  ifcond: Sequence[str] = (),
                   features: Sequence[QAPISchemaFeature] = ()) -> None:
         """
         Build and append a SchemaInfo object to self._trees.
@@ -302,7 +302,7 @@ def _gen_variant(self, variant: QAPISchemaVariant
 
     def visit_builtin_type(self, name: str, info: Optional[QAPISourceInfo],
                            json_type: str) -> None:
-        self._gen_tree(name, 'builtin', {'json-type': json_type}, [])
+        self._gen_tree(name, 'builtin', {'json-type': json_type})
 
     def visit_enum_type(self, name: str, info: Optional[QAPISourceInfo],
                         ifcond: Sequence[str],