Update ofxAndroidVideoPlayer.cpp

If the ofxAndroidVideoPlayer's texture is unloaded by "unloadTexture()" method,
and then if the Android app goes to pause state;

When returning to resume state, a Fatal Error is occuring because the unloaded (unavailable) texture cannot be reloaded.

Due to this bug I added:

    texture.texData.bAllocated = false;

line to the end of unloadTexture() method.