Fixed a problem with negative values in MidiMessage::getKeySignatureNumberOfSharpsOrFlats()

modules/juce_audio_basics/midi/juce_MidiMessage.cpp

@@ -841,7 +841,7 @@ bool MidiMessage::isKeySignatureMetaEvent() const noexcept
 
 int MidiMessage::getKeySignatureNumberOfSharpsOrFlats() const noexcept
 {
-    return (int) getMetaEventData()[0];
+    return (int) (int8) getMetaEventData()[0];
 }
 
 bool MidiMessage::isKeySignatureMajorKey() const noexcept