Fixed crash introduced in previous commit. The assumption was that `buffer.set_lexer` is only unavailable for the first buffer, which has `buffer:private_lexer_call(SETLEXERLANGUAGE, ...)` called in the `events.BUFFER_NEW` handler. However, `reset()` throws a wrench into everything and a buffer can end up without a lexer.
Fixed crash introduced in previous commit.
The assumption was that `buffer.set_lexer` is only unavailable for the first
buffer, which has `buffer:private_lexer_call(SETLEXERLANGUAGE, ...)` called in
the `events.BUFFER_NEW` handler. However, `reset()` throws a wrench into
everything and a buffer can end up without a lexer.

rgieseke/textadept,rgieseke/textadept