server/process: Fix logging issues where only the first message was displayed
    
    I realised only the first logging message was being displayed in a given
    parsing process. The reason turned out to be the UI handler failing
    with a "pop from empty list". The default handler was then lost and
    no further messages were processed.
    
    Fix this by catching the exception correctly in the connection writer code.
    
    Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>