fix for stateful mixin method isEqual which fails hard on array value compared with null.

[keyurpatel]

Version

2.2.3

Test Case

http://jsfiddle.net/fabricjs/Da7SP/

Steps to reproduce

Description
stateful mixin method isEqual throw an exception when it tries to compare an array value with null.

Generally when we use stroke

1. add an object
2. apply stroke from line stroke to dashed stroke.

here when the state has changed for an object it verifies using isEqual mixin method and returns a boolean value. But while checking it fails where original array value is [4,1] and the current value is null and not an array.

Expected Behavior

it should return false

Actual Behavior

currently, throw an exception in the console.

Error stack reference

[asturur]

this has been fixed right?