Fixed rcube_imap_generic::uncompressMessageSet() result when argument is empty. Added tests.

Conflicts:

	tests/Framework/ImapGeneric.php

program/include/rcube_imap_generic.php

@@ -3590,6 +3590,10 @@ class rcube_imap_generic
      */
     static function uncompressMessageSet($messages)
     {
+        if (empty($messages)) {
+            return array();
+        }
+
         $result   = array();
         $messages = explode(',', $messages);
 
@@ -3598,7 +3602,7 @@ class rcube_imap_generic
             $max   = max($items[0], $items[1]);
 
             for ($x=$items[0]; $x<=$max; $x++) {
-                $result[] = $x;
+                $result[] = (int)$x;
             }
             unset($messages[$idx]);
         }