AudioSampleBuffer::operator= isClear bug

Seems that creating an AudioSampleBuffer and setting it to another, non-clear buffer, does not turn of the isClear flag of the new buffer.

very simple fix: https://github.com/yairchu/JUCE/commit/de49d77af40083cceeb046805370892704acce25

Cheers, Yair

Drat! Thanks, will get that sorted out!