Preserve widgets from Loop 1.7.11 and lower versions

android/uhabits-core/src/main/java/org/isoron/uhabits/core/preferences/WidgetPreferences.java

@@ -38,7 +38,17 @@ public class WidgetPreferences {
     }
 
     public long[] getHabitIdsFromWidgetId(int widgetId) {
-        long habitIds[] = storage.getLongArray(getHabitIdKey(widgetId));
+        long habitIds[];
+        String habitIdKey = getHabitIdKey(widgetId);
+        try {
+            habitIds = storage.getLongArray(habitIdKey);
+        } catch (ClassCastException e) {
+            // Up to Loop 1.7.11, this preference was not an array, but a single
+            // long. Trying to read the old preference causes a cast exception.
+            habitIds = new long[1];
+            habitIds[0] = storage.getLong(habitIdKey, -1);
+            storage.putLongArray(habitIdKey, habitIds);
+        }
         if (habitIds.length == 0) throw new HabitNotFoundException();
         return habitIds;
     }