Retain scroll position when deleting messages

Removed the call to `refreshMessages()` as it's not really needed here and also because it'll reset the scroll position in some cases

app/src/main/kotlin/com/simplemobiletools/smsmessenger/activities/ThreadActivity.kt

@@ -408,6 +408,7 @@ class ThreadActivity : SimpleActivity() {
     }
 
     private fun deleteMessages(messagesToRemove: List<Message>) {
+        val deletePosition = threadItems.indexOf(messagesToRemove.first())
         messages.removeAll(messagesToRemove.toSet())
         threadItems = getThreadItems()
 
@@ -416,7 +417,7 @@ class ThreadActivity : SimpleActivity() {
                 finish()
             } else {
                 getOrCreateThreadAdapter().apply {
-                    updateMessages(threadItems)
+                    updateMessages(threadItems, scrollPosition = deletePosition)
                     finishActMode()
                 }
             }
@@ -441,7 +442,6 @@ class ThreadActivity : SimpleActivity() {
             updateScheduledMessagesThreadId(messages, fakeThreadId)
             threadId = fakeThreadId
         }
-        refreshMessages()
     }
 
     private fun fetchNextMessages() {

app/src/main/kotlin/com/simplemobiletools/smsmessenger/adapters/ThreadAdapter.kt

@@ -230,7 +230,9 @@ class ThreadAdapter(
     fun updateMessages(newMessages: ArrayList<ThreadItem>, scrollPosition: Int = newMessages.lastIndex) {
         val latestMessages = newMessages.toMutableList()
         submitList(latestMessages) {
-            recyclerView.scrollToPosition(scrollPosition)
+            if (scrollPosition != -1) {
+                recyclerView.scrollToPosition(scrollPosition)
+            }
         }
     }