Fix settings export as json (#498)

Root cause was that sometimes lists were List<string> but other times
they were List<dynamic>.
The fix was broadening the comparison to just List because all Lists
saved to shared prefs are in fact lists of string.

chameleonultragui/lib/sharedprefsprovider.dart

@@ -320,7 +320,7 @@ class SharedPreferencesProvider extends ChangeNotifier {
       if (value == null) {
         continue;
       }
-      if (value is List<String>) {
+      if (value is List) {
         // this hack is needed in order to output proper json with objects instead of objects-in-strings
         value = value.map((e) => jsonDecode(e)).toList();
       }