Disabled repeat combo in editor when in todo mode and when no due date set,...

Disabled repeat combo in editor when in todo mode and when no due date set, preventing a possible crash situation

src/contents/ui/IncidenceEditor.qml

@@ -381,6 +381,7 @@ Kirigami.ScrollablePage {
                     Kirigami.FormData.label: i18n("Repeat:")
                     Layout.fillWidth: true
 
+                    enabled: !incidenceForm.isTodo || !isNaN(root.incidenceWrapper.incidenceStart.getTime()) || !isNaN(root.incidenceWrapper.incidenceEnd.getTime())
                     textRole: "display"
                     valueRole: "interval"
                     onCurrentIndexChanged: if(currentIndex === 0) { root.incidenceWrapper.clearRecurrences() }