Fix regression in .ix fallback with IntervalIndex
closes #27865

cc @jbrockmendel this is another one from limiting the catched exceptions in https://github.com/pandas-dev/pandas/pull/27223/files#diff-7489e290a23303c4db4f803011ecaf8eR121. But also this time it's again rather a bug in the code that raises this error.

For some reason, `DataFrame._get_value` for a DataFrame with an IntervalIndex raises an AttributeError. That's a bug in itself which should be solved (and probably is the cause of more bugs in other places where `_get_value` is used, eg in `.at`). But will open a separate issue for that. 