[BUGFIX release] Allows @each to work with arrays that contain falsy …

…values

This matches the original behavior as seen in the each_proxy.

packages/@ember/-internals/metal/lib/chain-tags.ts

@@ -125,12 +125,14 @@ export function getChainTagsForKey(obj: any, path: string) {
       for (let i = 0; i < arrLength; i++) {
         let item = objectAt(current as Array<any>, i);
 
-        assert(
-          `When using @each to observe the array \`${current.toString()}\`, the items in the array must be objects`,
-          typeof item === 'object'
-        );
+        if (item) {
+          assert(
+            `When using @each to observe the array \`${current.toString()}\`, the items in the array must be objects`,
+            typeof item === 'object'
+          );
 
-        chainTags.push(tagForProperty(item, segment));
+          chainTags.push(tagForProperty(item, segment));
+        }
       }
 
       // Push the tag for the array length itself

packages/@ember/-internals/runtime/tests/system/object/computed_test.js

@@ -457,6 +457,28 @@ moduleFor(
       assert.deepEqual(n.normalized, []);
     }
 
+    ['@test @each works on array with falsy values'](assert) {
+      let obj = EmberObject.extend({
+        falsy: [null, undefined, false, '', 0, {}],
+        truthy: [true, 'foo', 123],
+
+        falsyComputed: computed('[email protected]', () => {
+          assert.ok(true, 'falsy computed');
+        }),
+
+        truthyComputed: computed('[email protected]', () => {
+          assert.ok(true, 'truthy computed');
+        }),
+      }).create();
+
+      // should throw no errors
+      obj.falsyComputed;
+
+      expectAssertion(() => {
+        obj.truthyComputed;
+      }, /When using @each to observe the array `true,foo,123`, the items in the array must be objects/);
+    }
+
     ['@test @each works with array-likes'](assert) {
       class ArrayLike {
         constructor(arr = []) {