diff --git a/app/js/filters/list-filters.js b/app/js/filters/list-filters.js
index 28db718..5ef0c7e 100644
--- a/app/js/filters/list-filters.js
+++ b/app/js/filters/list-filters.js
@@ -3,36 +3,64 @@
 var filtersModule = require('./_index.js');
 
 var split = function(input, delim) {
+  if (typeof input === 'undefined' || input === null) {
+    return [];
+  }
+
   delim = delim || ',';
 
   return input.split(delim);
 };
 
 var join = function(input, delim) {
+  if (typeof input === 'undefined' || input === null) {
+    return '';
+  }
+
   delim = delim || ', ';
 
   return input.join(delim);
 };
 
 var pick = function(input, index) {
+  if (typeof input === 'undefined' || input === null) {
+    return '';
+  }
+
   return input[index];
 };
 
 var pickRight = function(input, index) {
+  if (typeof input === 'undefined' || input === null) {
+    return '';
+  }
+
   return input[input.length - index];
 };
 
 var slice = function(input, begin, end) {
+  if (typeof input === 'undefined' || input === null) {
+    return [];
+  }
+
   return input.slice(begin, end);
 };
 
 var first = function(input, length) {
+  if (typeof input === 'undefined' || input === null) {
+    return '';
+  }
+
   length = length || 1;
 
   return input.slice(0, input.length - length);
 };
 
 var last = function(input, length) {
+  if (typeof input === 'undefined' || input === null) {
+    return '';
+  }
+
   length = length || 1;
 
   return input.slice(input.length - length, input.length);