#1079 Don't call wxChoice::GetString() with wxNOT_FOUND

[Miguel Gimenez]

The upcoming wx3.1.5 will assert when calling wxChoice::GetString(wxNOT_FOUND). The file manager plugin calls GetString(GetSelection()) from two places without checking if the selection is valid, so it is getting assertions with current wxMaster.

See wxWidgets 3.1.5 for the discussion.

The attached patch fixes this .

[Morten MacFly]

Applied in SVN. Thank you!