fix @import not working. Better error message for empty response

lib/less/browser.js

@@ -286,12 +286,3 @@ function error(e, href) {
     }
 }
 
-//
-// Used by `@import` directives
-//
-less.Parser.importer = function (path, paths, callback) {
-    loadStyleSheet({ href: path, title: path }, function (root) {
-        callback(root);
-    });
-};
-

lib/less/parser.js

@@ -927,5 +927,14 @@ less.Parser = function Parser(env) {
     };
 };
 
-less.Parser.importer = null;
+if (typeof(window) !== 'undefined') {
+    //
+    // Used by `@import` directives
+    //
+    less.Parser.importer = function (path, paths, callback) {
+        loadStyleSheet({ href: path, title: path }, function (root) {
+            callback(root);
+        });
+    };
+}
 

lib/less/tree/import.js

@@ -28,6 +28,9 @@ tree.Import = function (path, imports) {
     // Only pre-compile .less files
     if (! this.css) {
         imports.push(this.path, function (root) {
+            if (! root) {
+                throw new(Error)("Error parsing " + that.path);
+            }
             that.root = root;
         });
     }