function supportsKey should behave the same way whenever keyboard config value is 'null' or 'undefined'

I'm submitting a ... [ ] bug report [x] feature request [ ] question about the decisions made in the repository
Do you want to request a feature or report a bug? feature function supportsKey(keyCode: number, config: Array) should behave the same way whenever config value is 'null' or 'undefined'. Case: modal dialog has no keyboard config setted.
```
export function supportsKey(keyCode: number, config: Array<number>): boolean {
if (!Array.isArray(config)) return config === null ? false : true;
return config.indexOf(keyCode) > -1;
}
```

That is what i do on dialog creation to workaround it:

if (dialogRef.context.keyboard === undefined) {
        dialogRef.context.keyboard = [27];
    }

What is the current behavior? Modal dialog closing on any key press if dialogRef.context.keyboard is not defined

ModalOverlay.prototype.documentKeypress = function (event) {
        // check that this modal is the last in the stack.
        if (!this.dialogRef.overlay.isTopMost(this.dialogRef))
            return;
        if (supportsKey(event.keyCode, /** @type {?} */ (this.dialogRef.context.keyboard))) {
            this.dialogRef.dismiss();
        }
    };

function supportsKey(keyCode, config) {
    if (!Array.isArray(config))
        return config === null ? false : true;
    return config.indexOf(keyCode) > -1;
}

What is the expected behavior? Do not close modal on any key by default (keyboard config is null or undefined)
What is the motivation / use case for changing the behavior? I'm implementing custom modal plugin that has no keyboard behave. The problem is by default any modal closing on any keypress.
Please tell us about your environment:
Angular version: 5.0.1
Browser: [all]

Code sample:

import { combineLatest } from 'rxjs/operator/combineLatest';
import { Injectable } from '@angular/core';

import {
  ContainerContent,
  Overlay,
  DialogRef,
  Modal as Modal_,
  CSSBackdrop,
  PromiseCompleter
} from 'ngx-modialog';

import { LimeModalContainer } from './modal-container.component';

import { OneButtonPresetBuilder } from './presets/one-button-preset';
import { TwoButtonPresetBuilder, PromptPresetBuilder } from './presets/two-button-preset';

@Injectable()
export class Modal extends Modal_ {
  constructor(overlay: Overlay) {
    super(overlay);
  }

  alert(): OneButtonPresetBuilder {
    return new OneButtonPresetBuilder(this, <any>{isBlocking: false});
  }

  prompt(): PromptPresetBuilder {
    return new PromptPresetBuilder(this, <any>{isBlocking: true, keyboard: null});
  }

  confirm(): TwoButtonPresetBuilder {
    return new TwoButtonPresetBuilder(this, <any>{isBlocking: true, keyboard: null});
  }

  protected create(dialogRef: DialogRef<any>, content: ContainerContent): DialogRef<any> {

    const backdropRef = this.createBackdrop(dialogRef, CSSBackdrop);
    const containerRef = this.createContainer(dialogRef, LimeModalContainer, content);

    let overlay = dialogRef.overlayRef.instance;
    let backdrop = backdropRef.instance;
    let container = containerRef.instance;

    dialogRef.inElement ? overlay.insideElement() : overlay.fullscreen();

    if (containerRef.location.nativeElement) {
      containerRef.location.nativeElement.focus();
    }

    if (dialogRef.context.keyboard === undefined) {
        dialogRef.context.keyboard = [27];
    }

    return dialogRef;
  }
}

shlomiassaf / ngx-modialog

function supportsKey should behave the same way whenever keyboard config value is 'null' or 'undefined' #412