Improve QVectorsWidget warning highlighting

[MBartkowiakSTFC]

Description of work
QVectorsWidget has an extra feature of setting and clearing errors if the inputs in the vector parameter table are invalid. This needed to be updated to account for the possibility of a warning being set in the underlying configurator.

closes #1201

Fixes

1. Reset the warning after clearing the input errors in the widget.

To test
Try to reproduce the problem from the issue. The warning should stay marked in the GUI.

[ChiCheng45]

Its better but there is still the issue where the highlighting can get cleared when you change some other option e.g. weights.

[MBartkowiakSTFC]

Its better but there is still the issue where the highlighting can get cleared when you change some other option e.g. weights.

Thanks for catching this one. I'll check if I can fix it too.

[MBartkowiakSTFC]

I think this should work now.

[ChiCheng45]

One last thing.

The run button is disabled, which is right, but highlighted yellow. It's fine, but usually it's not highlighted yellow when other configurators are in an error state. Happy to approve if you think its ok.

[MBartkowiakSTFC]

The RUN! button should be yellow whenever we have a warning in any of the widgets. It should be disabled when we have a widget with an error. So far, so good.

The q vectors widget creates a warning if one or more of the q-vector shells are empty, and an error if they are all empty. So, it is not possible for it to trigger this specific error without triggering this warning as well. I checked that invalid inputs in the parameter table trigger an error without a warning.

So, I think it's OK.

[ChiCheng45]

Looks good.