[PATCH[ log: Do not BUG_ON in log_first_err
[PATCH[ log: Do not BUG_ON in log_first_err

It turned out that calling log_first_error() is possible w/o
calling log_keep_first_err(), so don't bug_on() on it, just
return NULL.

Reported-by: Adrian Reber <a1b909ec1cc11cce40c28d3640eab600e582f833@lisas.de>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@virtouzzo.com>
Reviewed-by: Adrian Reber <a1b909ec1cc11cce40c28d3640eab600e582f833@lisas.de>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@virtuozzo.com>

eabatalov/criu,eabatalov/criu,eabatalov/criu,eabatalov/criu,eabatalov/criu,eabatalov/criu