VirtualKeyboard: At least for now avoid GSOD for utf-8 ussues

For example with Russian texts we could have a GSOD. Now incompatible
charachters from the input string are ignored.

See discussion here: http://openpli.org/forums/topic/31087-virtualkeyboardpy/
Avoid GSOD with VirtualKeyboard regards to UTF-8 issues
ChannelSelection: Add sanity chech in correctChannelNumber
Merge remote-tracking branch 'pli/master'