Disable write-ahead log on SQLite

Android 9 (Pie) silently introduced a new behavior where new SQLite
databases have Write-Ahead Logs (WALs) enabled by default. The data,
even after committed, is not written to the main database file until
later. This caused a silent bug leading to data loss, where exported
backups would either be empty or miss some recent data.

android/uhabits-android/src/main/java/org/isoron/uhabits/HabitsDatabaseOpener.kt

@@ -34,13 +34,20 @@ class HabitsDatabaseOpener(
 ) : SQLiteOpenHelper(context, databaseFilename, null, version) {
 
     override fun onCreate(db: SQLiteDatabase) {
+        db.disableWriteAheadLogging()
         db.version = 8
         onUpgrade(db, -1, version)
     }
 
+    override fun onOpen(db: SQLiteDatabase) {
+        super.onOpen(db)
+        db.disableWriteAheadLogging()
+    }
+
     override fun onUpgrade(db: SQLiteDatabase,
                            oldVersion: Int,
                            newVersion: Int) {
+        db.disableWriteAheadLogging()
         if (db.version < 8) throw UnsupportedDatabaseVersionException()
         val helper = MigrationHelper(AndroidDatabase(db))
         helper.migrateTo(newVersion)

android/uhabits-android/src/main/java/org/isoron/uhabits/tasks/ExportDBTask.java

@@ -66,7 +66,7 @@ public class ExportDBTask implements Task
         }
         catch (IOException e)
         {
-            e.printStackTrace();
+            throw new RuntimeException(e);
         }
     }