fix crash in history export

[bgruening]

Traceback (most recent call last): File "/opt/galaxy/venv/lib64/python3.8/site-packages/celery/app/trace.py", line 451, in trace_task R = retval = fun(*args, kwargs) File "/opt/galaxy/venv/lib64/python3.8/site-packages/celery/app/trace.py", line 734, in __protected_call return self.run(*args, **kwargs) File "/opt/galaxy/server/lib/galaxy/celery/init__.py", line 163, in wrapper rval = app.magic_partial(func)(*args, kwds) File "/opt/galaxy/venv/lib64/python3.8/site-packages/lagom/wrapping.py", line 28, in _bound_func return inner_func(*bound_args, *bound_kwargs) File "/opt/galaxy/venv/lib64/python3.8/site-packages/lagom/wrapping.py", line 45, in _error_handling_func return func(args, **kwargs) File "/opt/galaxy/server/lib/galaxy/celery/tasks.py", line 302, in prepare_history_download model_store_manager.prepare_history_download(request) File "/opt/galaxy/server/lib/galaxy/managers/model_stores.py", line 108, in prepare_history_download history = self._history_manager.by_id(request.history_id) File "/opt/galaxy/server/lib/galaxy/managers/base.py", line 359, in by_id id_filter = self.model_class.table.c.id == id AttributeError: type object 'History' has no attribute 'table'

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[github-actions[bot]]

This PR was merged without a "kind/" label, please correct.