Issue with angular 2 ngControl's minlength errors validator

I have faced the same problem, i.e. TypeError: Cannot read property 'minlength' of null. For me, the solution proposed by @yurzui solved the problem. I am adding it as an answer here (as suggested by @günter-zöchbauer), so that others (who may not read the comments) can easily find it.

Problem:

The minlength property may be accessed, before errors is defined:

<div *ngIf="firstName.errors.minlength">
    Too short
</div>

Solution:

Use the ? operator to ensure that errors is defined, before accessing its minglength property:

<div *ngIf="firstName.errors?.minlength">
    Too short
</div> 

Alternative Solution:

Wrap your div in another div that checks if errors is defined:

<div *ngIf="firstName.errors">
    <div *ngIf="firstName.errors.minlength">
        Too short
    </div> 
</div>

Note that both solutions assume that firstName is defined.

PS: For anyone who needs it, the same applies to errors.maxlength as well!