From c68d33f94ef6d6327be3dd98503d52405d003d2d Mon Sep 17 00:00:00 2001
From: Luke Page <luke.a.page@gmail.com>
Date: Sat, 1 Sep 2012 14:44:22 +0100
Subject: [PATCH] tighten up two if statements to stop exception in browser
 mode. fixes #807

---
 lib/less/parser.js   | 2 +-
 lib/less/tree/url.js | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/less/parser.js b/lib/less/parser.js
index 4fbb00d6..8deca014 100644
--- a/lib/less/parser.js
+++ b/lib/less/parser.js
@@ -639,7 +639,7 @@ less.Parser = function Parser(env) {
 
                     expect(')');
 
-                    return new(tree.URL)((value.value || value.data || value instanceof tree.Variable)
+                    return new(tree.URL)((value.value != null || value.data || value instanceof tree.Variable)
                                         ? value : new(tree.Anonymous)(value), imports.paths);
                 },
 
diff --git a/lib/less/tree/url.js b/lib/less/tree/url.js
index dc9b2159..df949064 100644
--- a/lib/less/tree/url.js
+++ b/lib/less/tree/url.js
@@ -5,7 +5,7 @@ tree.URL = function (val, paths) {
         this.attrs = val;
     } else {
         // Add the base path if the URL is relative and we are in the browser
-        if (typeof window !== 'undefined' && val.value && !/^(?:https?:\/\/|file:\/\/|data:|\/)/.test(val.value) && paths.length > 0) {
+        if (typeof window !== 'undefined' && typeof val.value === "string" && !/^(?:https?:\/\/|file:\/\/|data:|\/)/.test(val.value) && paths.length > 0) {
             val.value = paths[0] + (val.value.charAt(0) === '/' ? val.value.slice(1) : val.value);
         }
         this.value = val;