Fix binding from external Fact changes

src/FactSystem/FactControls/FactCheckBox.qml

@@ -7,14 +7,20 @@ import QGroundControl.Palette 1.0
 import QGroundControl.Controls 1.0
 
 QGCCheckBox {
+    checkedState: isFactChecked()
+
     property Fact fact: Fact { }
+
     property variant checkedValue:   1
     property variant uncheckedValue: 0
-    checkedState: fact ?
-                      (fact.typeIsBool ?
-                           (fact.value === false ? Qt.Unchecked : Qt.Checked) :
-                           (fact.value === 0 ? Qt.Unchecked : Qt.Checked)) :
-                      Qt.Unchecked
+
+    Binding on checkedState {
+        value: fact ?
+                   (fact.typeIsBool ?
+                        (fact.value === false ? Qt.Unchecked : Qt.Checked) :
+                        (fact.value === 0 ? Qt.Unchecked : Qt.Checked)) :
+                   Qt.Unchecked
+    }
 
     onClicked: fact.value = (checked ? checkedValue : uncheckedValue)
 }