play: Always check arg count and init keymap.

Currently we miss to do so if the config file does not exist or
is empty. This triggers the following assertion if, in addition,
no non-option arguments given:

        para_play: string.c:62: para_malloc: Assertion `size' failed.

This is because we try to allocate a zero sized buffer in main() due
to lls_num_inputs() returning 0. Fix this by changing the target of
the goto in handle_help_flags().

This bug was introduced during the conversion to lopsub.