FIX: Having a series of empty brackets would have markdown-js output

funky looking javascript `toString()` information.

Author: eviltrout

src/dialects/gruber.js

@@ -682,12 +682,14 @@ define(['../markdown_helpers', './dialect_helpers', '../parser'], function (Mark
           // [links][] uses links as its reference
           attrs = { ref: ( m[ 1 ] || String(children) ).toLowerCase(),  original: orig.substr( 0, consumed ) };
 
-          link = [ "link_ref", attrs ].concat( children );
+          if (children && children.length > 0) {
+            link = [ "link_ref", attrs ].concat( children );
 
-          // We can't check if the reference is known here as it likely wont be
-          // found till after. Check it in md tree->hmtl tree conversion.
-          // Store the original so that conversion can revert if the ref isn't found.
-          return [ consumed, link ];
+            // We can't check if the reference is known here as it likely wont be
+            // found till after. Check it in md tree->hmtl tree conversion.
+            // Store the original so that conversion can revert if the ref isn't found.
+            return [ consumed, link ];
+          }
         }
 
         // Another check for references

test/features/links/broken_brackets.json

@@ -0,0 +1,3 @@
+["html",
+  ["p", "[[][]"]
+]

test/features/links/broken_brackets.text

@@ -0,0 +1 @@
+[[][]