Using disabled property with context watchdog causes a crash

[scofalik]

Watchdog crashes when ckeditor component is initialized with disabled property and watchdog property together.

Below code is fired when disabled property of the component is read:

public setDisabledState( isDisabled: boolean ): void {
	// If already initialized.
	if ( this.editorInstance ) {
		this.editorInstance.isReadOnly = isDisabled;
	}

	// Store the state anyway to use it once the editor is created.
	this.initialIsDisabled = isDisabled;
}

this.editorInstance is a getter:

public get editorInstance(): CKEditor5.Editor | null {
	if ( this.editorWatchdog ) {
		return this.editorWatchdog.editor;
	}

	if ( this.watchdog ) {
		return this.watchdog.getItem( this.id );
	}

	return null;
}

Unfortunately, at the time setDisabledState is called, the editor is not yet added to the watchdog, so this.watchdog.getItem throws an error.

[ma2ciek]

In the next iteration we should close the ckeditor/ckeditor5#6461 and use the new API.