Revert "Auto link broken threads"

This reverts commit 8af8641089.

app/src/main/java/eu/faircode/email/DaoMessage.java

@@ -587,9 +587,6 @@ public interface DaoMessage {
     @Query("UPDATE message SET revisions = :revisions WHERE id = :id")
     int setMessageRevisions(long id, Integer revisions);
 
-    @Query("UPDATE message SET thread = :thread WHERE id = :id")
-    int setMessageThread(long id, String thread);
-
     @Query("UPDATE message" +
             " SET content = 0, fts = 0, language = NULL, plain_only = NULL, preview = NULL" +
             " WHERE id = :id")

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -873,19 +873,12 @@ public class MessageHelper {
         if (!TextUtils.isEmpty(inreplyto) && !refs.contains(inreplyto))
             refs.add(inreplyto);
 
-        String thread = null;
         DB db = DB.getInstance(context);
         for (String ref : refs) {
             List<EntityMessage> messages = db.message().getMessagesByMsgId(account, ref);
-            for (EntityMessage message : messages) {
-                if (thread == null)
-                    thread = message.thread;
-                if (thread != null && !thread.equals(message.thread))
-                    db.message().setMessageThread(message.id, thread);
-            }
+            if (messages.size() > 0)
+                return messages.get(0).thread;
         }
-        if (thread != null)
-            return thread;
 
         if (refs.size() > 0)
             return refs.get(0);