- Fix: skip redundant cache queries when an entry doesn't exist

program/include/rcube_cache.php

@@ -245,6 +245,7 @@ class rcube_cache
             return null;
         }
 
+        if ($this->type != 'db') {
             if ($this->type == 'memcache') {
                 $data = $this->db->get($this->ckey($key));
             }
@@ -263,8 +264,11 @@ class rcube_cache
                 $this->cache_sums[$key] = $md5sum;
                 $this->cache[$key]      = $data;
             }
-
-        if ($this->type == 'db') {
+            else if (!$nostore) {
+                $this->cache[$key] = null;
+            }
+        }
+        else {
             $sql_result = $this->db->limitquery(
                 "SELECT cache_id, data, cache_key".
                 " FROM ".get_table_name('cache').
@@ -290,6 +294,9 @@ class rcube_cache
 	            $this->cache_sums[$key] = $md5sum;
                 $this->cache_keys[$key] = $sql_arr['cache_id'];
             }
+            else if (!$nostore) {
+                $this->cache[$key] = null;
+            }
         }
 
         return $this->cache[$key];