Merge pull request #776 from naveensingh/fix_threading_crash

Execute `clearAllMessagesIfNeeded` callback on the main thread

app/src/main/kotlin/com/simplemobiletools/smsmessenger/extensions/Context.kt

@@ -1038,7 +1038,7 @@ fun Context.clearAllMessagesIfNeeded(callback: () -> Unit) {
         ensureBackgroundThread {
             messagesDB.deleteAll()
             config.wasDbCleared = true
-            callback()
+            Handler(Looper.getMainLooper()).post(callback)
         }
     } else {
         callback()