fixed reset of (welpen) spur gefunden on page switch

lib/screens/excursion/widgets/spur_gefunden.dart

@@ -26,10 +26,22 @@ class SpurGefunden extends StatefulWidget {
 }
 
 class _SpurGefundenState extends State<SpurGefunden> {
-  bool _spurFundChecked = false;
+  late bool _spurFundChecked;
   // bool _spSicher = false;
   // bool _wpSicher = false;
-  bool _welpenSp = false;
+  late bool _welpenSpFundChecked;
+
+  @override
+    void initState() {
+      if (widget.spurFund.text == "") {
+        _spurFundChecked = false;
+        _welpenSpFundChecked = false;
+      } else {
+        _spurFundChecked = true;
+        _welpenSpFundChecked = true;
+      }
+      super.initState();
+    }
 
   @override
   Widget build(BuildContext context) {
@@ -49,10 +61,10 @@ class _SpurGefundenState extends State<SpurGefunden> {
             ),
             Text(AppLocalizations.of(context)!.welpenSpurGefunden),
             Checkbox(
-              value: _welpenSp,
+              value: _welpenSpFundChecked,
               onChanged: (val) {
                 setState(() {
-                  _welpenSp = val ?? false;
+                  _welpenSpFundChecked = val ?? false;
                   widget.welpenSp.text = val ?? false ? "WelpenSp" : "";
                 });
               },