### JerryScript revision
2.4.0

### Build platform
ubuntu20.04

### Description
I found jerryscript can not output correctly like other js engines when I ran the following code. However when I set the length to 0xfff or 0xfffff, it can print. 

### Test case
``` javascript
var a = ['a'];
var b = [];
b.length = 0xffff;
c = a.concat(b);
print(c.length);
```

### Output

### Expected behavior
65536

A bug in concat()
This is a GitHub Issue
repo:jerryscript
owner:jerryscript-project
Title : A bug in concat()
Issue date:

--- start body ---
### JerryScript revision
2.4.0

### Build platform
ubuntu20.04

### Description
I found jerryscript can not output correctly like other js engines when I ran the following code. However when I set the length to 0xfff or 0xfffff, it can print. 

### Test case
``` javascript
var a = ['a'];
var b = [];
b.length = 0xffff;
c = a.concat(b);
print(c.length);
```

### Output

### Expected behavior
65536

--- end body ---
