Fixed a bug in the implementation of "comparable".

functions.cpp

@@ -563,9 +563,15 @@ namespace Sass {
           return F;
         }
       }
-      else {
+      else if (!n1.is_numeric() && !n2.is_numeric()) {
         eval_error("arguments to comparable must be numeric", n1.line_number, n1.file_name);
       }
+      else {
+        Node F(Node::boolean);
+        F.line_number = n1.line_number;
+        F.content.boolean_value = false;
+        return F;
+      }
     }
     
     // Boolean Functions ///////////////////////////////////////////////////