Hello, I am trying connecting Redshift spectrum but unable to add the tables throwing below exception, but at the same time if a table is created in Redshift (not as Spectrum) successfully able to add the same, any help will be really appreciate\n```ERROR:superset.views.base:Got an error in pre_add for extension_db_redshift.navigation\nTraceback (most recent call last):\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy_redshift/dialect.py", line 691, in _get_redshift_relation\n    return all_relations[key]\nKeyError: 'extension_db_redshift.navigation'\n\nDuring handling of the above exception, another exception occurred:\n\nTraceback (most recent call last):\n  File "/app/superset/views/base.py", line 213, in validate_sqlatable\n    table.get_sqla_table_object()\n  File "/app/superset/connectors/sqla/models.py", line 1176, in get_sqla_table_object\n    return self.database.get_table(self.table_name, schema=self.schema)\n  File "/app/superset/models/core.py", line 613, in get_table\n    autoload_with=self.get_sqla_engine(),\n  File "&lt;string&gt;", line 2, in __new__\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/util/deprecations.py", line 128, in warned\n    return fn(*args, **kwargs)\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/sql/schema.py", line 506, in __new__\n    metadata._remove_table(name, schema)\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/util/langhelpers.py", line 68, in __exit__\n    compat.reraise(exc_type, exc_value, exc_tb)\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 153, in reraise\n    raise value\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/sql/schema.py", line 501, in __new__\n    table._init(name, metadata, *args, **kw)\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/sql/schema.py", line 595, in _init\n    resolve_fks=resolve_fks,\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/sql/schema.py", line 619, in _autoload\n    _extend_on=_extend_on,\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 2160, in run_callable\n    return conn.run_callable(callable_, *args, **kwargs)\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1612, in run_callable\n    return callable_(self, *args, **kwargs)\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 459, in reflecttable\n    table, include_columns, exclude_columns, resolve_fks, **opts\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/reflection.py", line 629, in reflecttable\n    table_name, schema, **table.dialect_kwargs\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/reflection.py", line 314, in get_table_options\n    self.bind, table_name, schema, info_cache=self.info_cache, **kw\n  File "&lt;string&gt;", line 2, in get_table_options\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/engine/reflection.py", line 56, in cache\n    ret = fn(self, con, *args, **kw)\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy_redshift/dialect.py", line 606, in get_table_options\n    schema, **kw)\n  File "/usr/local/lib/python3.6/site-packages/sqlalchemy_redshift/dialect.py", line 693, in _get_redshift_relation\n    raise sa.exc.NoSuchTableError(key)```\n