Some more debug

Author: mishanga

lib/csscomb.js

@@ -85,11 +85,18 @@ Comb.prototype = {
      */
     processString: function(text, filename) {
         var tree;
+        var string = JSON.stringify;
+        if (typeof text === 'undefined') {
+            throw new Error('Undefined file content ' + filename + ': ' + string(text));
+        }
         try {
             tree = gonzales.srcToCSSP(text);
         } catch (e) {
             throw new Error('Parsing error at ' + filename + ': ' + e.message);
         }
+        if (typeof tree === 'undefined') {
+            throw new Error('Undefined tree at ' + filename + ': ' + string(text) + ' => ' + string(tree));
+        }
         tree = this.processTree(tree);
         return gonzales.csspToSrc(tree);
     },