diff --git a/plugins/context_reaction_block.js b/plugins/context_reaction_block.js
index 67e2031..76deb8a 100644
--- a/plugins/context_reaction_block.js
+++ b/plugins/context_reaction_block.js
@@ -70,6 +70,7 @@ DrupalContextBlockForm = function(blockForm) {
     // Show blocks in selector that are unused
     $('div.context-blockform-selector input').each(function() {
       var bid = $(this).val();
+      if (bid == '') return; //We check bid. If empty we just return.
       if ($('table.context-blockform-region tr#'+bid).size() === 0) {
         $(this).parents('div.form-item').eq(0).show();
       }