[REWORK] Crash for file open error case is fixed in file logger
[REWORK] Crash for file open error case is fixed in file logger

It was a bug which may be cause of crash in case file open error
(iFp == 0 after fopen). This bug is fixed in this commit.
Also log_warnings are added to inform about such incident.

nemomobile-graveyard/libqmlog,nemomobile-graveyard/libqmlog,nemomobile-graveyard/libqmlog