HyperSpectra: invalid contexts can be matched to a data (and thus the widget crashes)

[markotoplak]

HyperSpectra has comboboxes to choose feature. Some of the accept all features, and some are limited to metas and classes.

All these settings are linked to a DomainContextHandler. Therefore, old settings could cause newly connected data to crash because of biolab/orange3#6721.

This was originally reported by @clsandt.

The workaround is to clear the settings (Options -> Reset widget settings) and, then, add a new widget instance.