Add space between classes in HTMLButtonField

Classes such as 'wb-input-buttonmw-ui-button' were being generated
when $wgUseMediaWikiUIEverywhere = true, see:
https://integration.wikimedia.org/ci/job/mwext-Wikibase-repo-tests-mysql-hhvm/4217/console

Change-Id: If40b712ffb8e31d27380bf481333eecb7b95f9de

diff --git a/includes/htmlform/HTMLButtonField.php b/includes/htmlform/HTMLButtonField.php
index b0b08a6..56a23ad 100644 (file)
--- a/includes/htmlform/HTMLButtonField.php
+++ b/includes/htmlform/HTMLButtonField.php
@@ -28,7 +28,7 @@ class HTMLButtonField extends HTMLFormField {
                ) {
                        $prefix = 'mw-ui-';
                        // add mw-ui-button separately, so the descriptor doesn't need to set it
-                       $flags .= $prefix.'button';
+                       $flags .= ' ' . $prefix.'button';
                }
                foreach ( $this->mFlags as $flag ) {
                        $flags .= ' ' . $prefix . $flag;