WebDAV::exists() should add a trailing slash for checking dirs

Without it, some WebDAV servers will thrown an error.

code/utils/WebDAV.php

@@ -13,6 +13,11 @@ class WebDAV {
 	}
 
 	static function exists($url) {
+		// WebDAV expects that checking a directory exists has a trailing slash
+		if (substr($url, -1) != '/') {
+			$url .= '/';
+		}
+
 		$ch = self::curl_init($url, 'PROPFIND');
 		
 		$res = curl_exec($ch);
@@ -60,4 +65,4 @@ class WebDAV {
 	}
 
 
-}
+}