Use empty array instead of sentinel value -1 as habitId

uhabits-android/src/main/java/org/isoron/uhabits/widgets/BaseWidgetProvider.kt

@@ -109,7 +109,7 @@ abstract class BaseWidgetProvider : AppWidgetProvider() {
     }
 
     protected fun getHabitsFromWidgetId(widgetId: Int): List<Habit> {
-        val selectedIds = widgetPrefs.getHabitIdsFromWidgetId(widgetId)!!
+        val selectedIds = widgetPrefs.getHabitIdsFromWidgetId(widgetId)
         val selectedHabits = ArrayList<Habit>(selectedIds.size)
         for (id in selectedIds) {
             val h = habits.getById(id) ?: throw HabitNotFoundException()

uhabits-android/src/main/java/org/isoron/uhabits/widgets/WidgetUpdater.kt

@@ -95,7 +95,7 @@ class WidgetUpdater
         val modifiedWidgetIds = when (modifiedHabitId) {
             null -> widgetIds.toList()
             else -> widgetIds.filter { w ->
-                widgetPrefs.getHabitIdsFromWidgetId(w)!!.contains(modifiedHabitId)
+                widgetPrefs.getHabitIdsFromWidgetId(w).contains(modifiedHabitId)
             }
         }
 

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/preferences/Preferences.kt

@@ -258,7 +258,7 @@ open class Preferences(private val storage: Storage) {
             putString(key, joinLongs(values))
         }
 
-        fun getLongArray(key: String, defValue: LongArray): LongArray? {
+        fun getLongArray(key: String, defValue: LongArray): LongArray {
             val string = getString(key, "")
             return if (string.isEmpty()) defValue else splitLongs(
                 string

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/preferences/WidgetPreferences.kt

@@ -27,19 +27,18 @@ class WidgetPreferences @Inject constructor(private val storage: Preferences.Sto
         storage.putLongArray(getHabitIdKey(widgetId), habitIds)
     }
 
-    fun getHabitIdsFromWidgetId(widgetId: Int): LongArray? {
+    fun getHabitIdsFromWidgetId(widgetId: Int): LongArray {
-        var habitIds: LongArray?
         val habitIdKey = getHabitIdKey(widgetId)
-        try {
+        return try {
-            habitIds = storage.getLongArray(habitIdKey, longArrayOf(-1))
+            storage.getLongArray(habitIdKey, longArrayOf())
         } catch (e: ClassCastException) {
             // 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 = LongArray(1)
+            when (val habitId = storage.getLong(habitIdKey, -1)) {
-            habitIds[0] = storage.getLong(habitIdKey, -1)
+                -1L -> longArrayOf()
-            storage.putLongArray(habitIdKey, habitIds)
+                else -> longArrayOf(habitId)
+            }
         }
-        return habitIds
     }
 
     fun removeWidget(id: Int) {