Ignore empty when iterating on sparse arrays

Fixes #1065

lib/handlebars/helpers/each.js

@@ -25,6 +25,12 @@ export default function(instance) {
     }
 
     function execIteration(field, index, last) {
+      // Don't iterate over undefined values since we can't execute blocks against them
+      // in non-strict (js) mode.
+      if (context[field] == null) {
+        return;
+      }
+
       if (data) {
         data.key = field;
         data.index = index;

spec/regressions.js

@@ -196,4 +196,11 @@ describe('Regressions', function() {
 
     shouldCompileToWithPartials(root, [{}, helpers, partials], true, '<partial>');
   });
+
+  it('GH-1065: Sparse arrays', function() {
+    var array = [];
+    array[1] = 'foo';
+    array[3] = 'bar';
+    shouldCompileTo('{{#each array}}{{@index}}{{.}}{{/each}}', {array: array}, '1foo3bar');
+  });
 });