Handle case where there are no messages

app/src/main/java/org/thoughtcrime/securesms/database/MmsSmsDatabase.java

@@ -325,9 +325,12 @@ public class MmsSmsDatabase extends Database {
     String selection = MmsSmsColumns.THREAD_ID + " = " + threadId;
 
     try (Cursor cursor = queryTables(PROJECTION, selection, order, "1")) {
-      cursor.moveToFirst();
-      return cursor.getLong(cursor.getColumnIndexOrThrow(MmsSmsColumns.NORMALIZED_DATE_SENT));
+      if (cursor.moveToFirst()) {
+        return cursor.getLong(cursor.getColumnIndexOrThrow(MmsSmsColumns.NORMALIZED_DATE_SENT));
+      }
     }
+
+    return -1;
   }
 
   public Cursor getUnread() {

app/src/main/java/org/thoughtcrime/securesms/database/ThreadDatabase.java

@@ -939,7 +939,9 @@ public class ThreadDatabase extends Database {
       if (count > 0) {
         MmsSmsDatabase mmsSmsDatabase = DatabaseComponent.get(context).mmsSmsDatabase();
         long messageTimestamp = mmsSmsDatabase.getLastMessageTimestamp(threadId);
-        lastMessage = mmsSmsDatabase.getMessageForTimestamp(messageTimestamp);
+        if (messageTimestamp > 0) {
+          lastMessage = mmsSmsDatabase.getMessageForTimestamp(messageTimestamp);
+        }
       }
 
       return new ThreadRecord(body, snippetUri, lastMessage, recipient, date, count,