Handle invalid input to list filter functions safely.

Previously list filter functions did not handle invalid input safely.
This adds a check for null or undefined input and returns a default safe
value.

Change-Id: I59ea3be8b3d8413851204046890121bda3a44e04

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);