Cross-section widget: "As line" checkbox not reactivated after deactivation

[JoerivanEngelen]

@rubencalje reported the following issue, worthy its own issue:

The imod plugin performs really well, especially the Time Series and Cross Section widgets, and integrates well in QGIS. I have managed to get my data into the plugin, below is a screenshot of my project. I do have variables named 'toplayer{x}" and "bottomlayer{x}" for x from 1 to 28, and all layered variables are shown by a single checkbox in the variable selection list. However, I cannot uncheck the "As line(s)" checkbox, as it is disabled. Does this have anything to do with this issue?

More info, here in this issue https://github.com/Deltares/imod-qgis/issues/65

[JoerivanEngelen]

@rubencalje came up with a fix (thanks!) and asked how to name branch. We don't have very strong requirements on branch naming for imod-qgis, but for imod-python we normally do something like issue_<nr>_<very-brief-description>, so here that would be something like: issue_71_reactivate-checkbox-after-deactivation