[rbp/omxplayer] Fix divide by zero at eof

If you leave the codec info up in a debug build and reach eof, you will abort.

This is due to audio decoder being closed, which zeros m_BytesPerSec, but the player info is still requested.
GetCacheTime will do a divide by zero. This change protects that divide.
Merge pull request #2850 from popcornmix/fix_div_zero

[rbp/omxplayer] Fix divide by zero at eof