function onTextureDispose( event ) {

	const texture = event.target;

	texture.removeEventListener( 'dispose', onTextureDispose );

	const renderTarget = _cache$1.get( texture );

	if ( renderTarget !== undefined ) {

		_cache$1.delete( texture );

		renderTarget.dispose();

	}

}
This function is executed when `dispose()` is called on the equirectangular
texture. In this case, the generated cube map with its render target
is deleted as well.

@private
@param {Object} event - The event object.