Fixed Sticky Shift Conflict

Fixed conflict when Sticky Shift functionality is enabled with the Shift Acceleration that was added in SynthstromAudible#636

Fixed it by calling isButtonPressed instead of isShiftButtonPressed in order to check if the Shift button is actually being pressed rather than "stickily pressed."

src/deluge/gui/ui/sound_editor.cpp

@@ -650,7 +650,7 @@ ActionResult SoundEditor::horizontalEncoderAction(int32_t offset) {
 
 void SoundEditor::selectEncoderAction(int8_t offset) {
 
-	if (Buttons::isShiftButtonPressed()) {
+	if (Buttons::isButtonPressed(deluge::hid::button::SHIFT)) {
 		offset = offset * 5;
 	}