Fix db_mode check in insert_id()

program/include/rcube_mdb2.php

@@ -123,9 +123,11 @@ class rcube_mdb2
     {
         // Already connected
         if ($this->db_connected) {
-            // no replication, current connection is ok
+            // no replication, current connection is ok for read and write
-            if (empty($this->db_dsnr) || $this->db_dsnw == $this->db_dsnr)
+            if (empty($this->db_dsnr) || $this->db_dsnw == $this->db_dsnr) {
+                $this->db_mode = 'w';
                 return;
+            }
 
             // connected to read-write db, current connection is ok
             if ($this->db_mode == 'w')