owncloud: validate prefs value as an URL

plugins/owncloud/owncloud.php

@@ -57,7 +57,7 @@ class OwnCloud extends Plugin {
     print "<input dojoType=\"dijit.form.TextBox\" style=\"display : none\" name=\"plugin\" value=\"owncloud\">";
     print "<table width=\"100%\" class=\"prefPrefsList\">";
         print "<tr><td width=\"40%\">".__("Owncloud url")."</td>";
-	print "<td class=\"prefValue\"><input dojoType=\"dijit.form.ValidationTextBox\" required=\"1\" name=\"owncloud_url\" value=\"$value\"></td></tr>";
+	print "<td class=\"prefValue\"><input dojoType=\"dijit.form.ValidationTextBox\" required=\"1\" name=\"owncloud_url\" regExp='^(http|https)://.*' value=\"$value\"></td></tr>";
     print "</table>";
     print "<p><button dojoType=\"dijit.form.Button\" type=\"submit\">".__("Set value")."</button>";