Fix rcube_imap_cache in mode set to MESSAGE only

program/lib/Roundcube/rcube_imap_cache.php

@@ -612,6 +612,10 @@ class rcube_imap_cache
      */
     function remove_index($mailbox = null, $remove = false)
     {
+        if (!($this->mode & self::MODE_INDEX)) {
+            return;
+        }
+
         // The index should be only removed from database when
         // UIDVALIDITY was detected or the mailbox is empty
         // otherwise use 'valid' flag to not loose HIGHESTMODSEQ value
@@ -646,10 +650,14 @@ class rcube_imap_cache
     /**
      * Clears thread cache.
      *
-     * @param string  $mailbox     Folder name
+     * @param string $mailbox Folder name
      */
     function remove_thread($mailbox = null)
     {
+        if (!($this->mode & self::MODE_INDEX)) {
+            return;
+        }
+
         $this->db->query(
             "DELETE FROM {$this->thread_table}"
             ." WHERE `user_id` = ?"
@@ -704,6 +712,10 @@ class rcube_imap_cache
      */
     private function get_index_row($mailbox)
     {
+        if (!($this->mode & self::MODE_INDEX)) {
+            return;
+        }
+
         // Get index from DB
         $sql_result = $this->db->query(
             "SELECT `data`, `valid`"
@@ -731,8 +743,6 @@ class rcube_imap_cache
                 'modseq'     => $data[5],
             );
         }
-
-        return null;
     }
 
     /**
@@ -740,6 +750,10 @@ class rcube_imap_cache
      */
     private function get_thread_row($mailbox)
     {
+        if (!($this->mode & self::MODE_INDEX)) {
+            return;
+        }
+
         // Get thread from DB
         $sql_result = $this->db->query(
             "SELECT `data`"
@@ -764,8 +778,6 @@ class rcube_imap_cache
                 'uidnext'  => $data[3],
             );
         }
-
-        return null;
     }
 
     /**
@@ -774,6 +786,10 @@ class rcube_imap_cache
     private function add_index_row($mailbox, $sort_field,
         $data, $mbox_data = array(), $exists = false, $modseq = null)
     {
+        if (!($this->mode & self::MODE_INDEX)) {
+            return;
+        }
+
         $data = array(
             $this->db->encode($data, true),
             $sort_field,
@@ -826,6 +842,10 @@ class rcube_imap_cache
      */
     private function add_thread_row($mailbox, $data, $mbox_data = array(), $exists = false)
     {
+        if (!($this->mode & self::MODE_INDEX)) {
+            return;
+        }
+
         $data = array(
             $this->db->encode($data, true),
             (int) $this->skip_deleted,