import DebugAdapter only if @ember-data/debug package is present Fix e…

…mberjs#7053

packages/-ember-data/addon/index.js

@@ -18,7 +18,10 @@ import AdapterError, {
 } from '@ember-data/adapter/error';
 import JSONAPIAdapter from '@ember-data/adapter/json-api';
 import RESTAdapter from '@ember-data/adapter/rest';
-import DebugAdapter from '@ember-data/debug';
+
+import { has } from 'require';
+const HAS_DEBUG_PACKAGE = has('@ember-data/debug') || false;
+
 import Model, { attr, belongsTo, hasMany } from '@ember-data/model';
 import Serializer from '@ember-data/serializer';
 import { BooleanTransform, DateTransform, NumberTransform, StringTransform } from '@ember-data/serializer/-private';
@@ -85,7 +88,9 @@ DS.errorsArrayToHash = errorsArrayToHash;
 
 DS.Serializer = Serializer;
 
-DS.DebugAdapter = DebugAdapter;
+if (HAS_DEBUG_PACKAGE) {
+  DS.DebugAdapter = require('@ember/debug').default;
+}
 
 DS.RecordArray = RecordArray;
 DS.AdapterPopulatedRecordArray = AdapterPopulatedRecordArray;