25fcb85590
A '-' keypress doesn't collapse a tree item with the native MSW tree
control. Instead, when not using the generic tree control, simulate a
keypress of WXK_LEFT to collapse the root item . This fixes the assert
checking if the root item is collapsed after the keypress.
Regression since 9d7a7ec556 (which
mistakenly may have had treectrltest.cpp as part of its commit).