midi pattern: prevent parameter changes when ui opens up

Signed-off-by: falkTX <falktx@falktx.com>

source/frontend/midipattern-ui

@@ -220,7 +220,9 @@ class MidiPatternW(ExternalUI, QMainWindow):
     # Custom callback
 
     def updateMeasureBox(self, index):
+        self.ui.measureBox.blockSignals(True)
         self.ui.measureBox.setCurrentIndex(index-1)
+        self.ui.measureBox.blockSignals(False)
 
     def sendMsg(self, data):
         msg = data[0]