Small warning in latest MPE code

Just posting it here in case you guys missed it.

mpe/juce_MPENote.cpp: In member function ‘bool juce::MPENote::isValid() const’:
mpe/juce_MPENote.cpp:74:67: warning: comparison is always true due to limited range of data type [-Wtype-limits]
     return midiChannel > 0 && midiChannel <= 16 && initialNote >= 0 && initialNote <= 127;

initialNote in unsigned, so the '>= 0' comparison there is not needed.

Thanks. (Odd that we didn't see that in either Xcode or Visual Studio..)