Cannot read property 'concat' of undefined (upgrade 2.16.2)

Only change I made was upgrade from 2.14.2 -> 2.16.2 and now when I run tests, this error causes a couple tests to fail (everything else works):

test-module-for-component.js:334 TypeError: Cannot read property 'concat' of undefined
    at WrappedBuilder.compile (ember.debug.js:4042)
    at ComponentLayoutBuilder.compile (ember.debug.js:3935)
    at compileLayout (ember.debug.js:3916)
    at Cache._emberMetal.Cache.owner [as func] (ember.debug.js:17622)
    at Cache.get (ember.debug.js:25086)
    at Environment.getCompiledBlock (ember.debug.js:17693)
    at OutletComponentManager.layoutFor (ember.debug.js:15625)
    at ember.debug.js:2662
    at AppendOpcodes.evaluate (ember.debug.js:1016)
    at VM.next (ember.debug.js:8190)

Which is apparently this line:

One of the tests that fails looks like this:

import { moduleForComponent, test } from 'ember-qunit';
import hbs from 'htmlbars-inline-precompile';
import wait from 'ember-test-helpers/wait';

moduleForComponent('content-editable', 'Integration | Component | content editable', {
  integration: true
});

test('it renders', function(assert) {

  this.set('text', 'Here is some text');
  this.set('editing', 'true');

  // Template block usage:
  this.render(hbs`
    {{content-editable value=text editable=editing class="d-inline-block" title="Test" id="test"}}
  `);

  assert.equal(this.$().html().trim(), '<div title="Test" data-test-id="content-editable" id="test" class="d-inline-block -editable ember-view" contenteditable="true" style="color: rgb(65, 65, 65);">Here is some text</div>');
})

Any tips to help debug?

[rwjblue]

Closing for now (seems to have gone stale), happy to reopen if this is still an issue…

[rwjblue]

@atomkirk - Are you using ember-source (from npm) or are you consuming via Bower? If bower, you probably also want to rm -rf bower_components.