refresh sms history based on oldest sms loaded, ignoring mms

all mms are always loaded, the number of messages only concerns sms, so only reference sms to determine the oldest loaded message

this should load all sms messages when there are mms messages in between

Fixes: #535

Author: yparitcher

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

@@ -514,7 +514,8 @@ class ThreadActivity : SimpleActivity() {
             return
         }
 
-        val dateOfFirstItem = messages.first().date
+        val firstItem = messages.first{ !it.isMMS }
+        val dateOfFirstItem = firstItem.date
         if (oldestMessageDate == dateOfFirstItem) {
             allMessagesFetched = true
             return
@@ -524,7 +525,6 @@ class ThreadActivity : SimpleActivity() {
         loadingOlderMessages = true
 
         ensureBackgroundThread {
-            val firstItem = messages.first()
             val olderMessages = getMessages(threadId, true, oldestMessageDate)
                 .filter { message -> !messages.contains(message) }