Declare definition

Declare `definition` in `BelongsTo.prototype.destroy`

Author: Amir-61

lib/relation-definition.js

@@ -1366,9 +1366,10 @@ BelongsTo.prototype.destroy = function(options, cb) {
     cb = options;
     options = {};
   }
-  var modelTo = this.definition.modelTo;
+
+  var definition = this.definition; 
   var modelInstance = this.modelInstance;
-  var fk = this.definition.keyFrom;
+  var fk = definition.keyFrom;
 
   cb = cb || utils.createPromiseCallback();