GUI bugfix: use isChecked instead of checkState in BoolInput

Change-Id: I4896df13c117c6eeaaaaba80ca3da4b1982c3d9b
Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/31346
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

frappy/gui/inputwidgets.py

@@ -56,7 +56,7 @@ class BoolInput(QCheckBox):
         self.datatype = datatype
 
     def get_input(self):
-        return self.checkState()
+        return self.isChecked()
 
     def submit(self):
         self.submitted.emit()