Fixed issue where pressing F3 did not display the search pane when the decompiler text view had focus.

Previously, pressing F3 when the decompiler text view had focus did not
display the search pane. This is because F3 is also assigned to the find
next command. This has been addressed by allowing the key press to route
up the element tree if no search pattern has been entered.
Merge remote-tracking branch 'nblackburn77/master'