setCanonicalRecord should check for this.canonicalState, not this.inverseRecord

when calling setCanonicalRecord with null it should check for presence
of canonicalState instead of inverseRecord.

(cherry picked from commit 8400b9d)

Author: jsedlacek

addon/-private/system/relationships/state/belongs-to.js

@@ -33,8 +33,8 @@ BelongsToRelationship.prototype.setRecord = function(newRecord) {
 BelongsToRelationship.prototype.setCanonicalRecord = function(newRecord) {
   if (newRecord) {
     this.addCanonicalRecord(newRecord);
-  } else if (this.inverseRecord) {
-    this.removeCanonicalRecord(this.inverseRecord);
+  } else if (this.canonicalState) {
+    this.removeCanonicalRecord(this.canonicalState);
   }
   this.setHasData(true);
   this.setHasLoaded(true);