fix(graphql): clear project when end_time is UNSET (#3879)

src/phoenix/server/api/mutations/project_mutations.py

@@ -38,7 +38,7 @@ async def clear_project(self, info: Info[Context, None], input: ClearProjectInpu
             global_id=input.id, expected_type_name="Project"
         )
         delete_statement = delete(models.Trace).where(models.Trace.project_rowid == project_id)
-        if input.end_time is not None:
+        if input.end_time:
             delete_statement = delete_statement.where(models.Trace.start_time < input.end_time)
         async with info.context.db() as session:
             await session.execute(delete_statement)