unbindTexture() {

		const { gl, currentTextureSlot, currentBoundTextures } = this;

		const boundTexture = currentBoundTextures[ currentTextureSlot ];

		if ( boundTexture !== undefined && boundTexture.type !== undefined ) {

			gl.bindTexture( boundTexture.type, null );

			boundTexture.type = undefined;
			boundTexture.texture = undefined;

		}

	}
Unbinds the current bound texture.

This method caches the state so `gl.bindTexture()` is only
called when necessary.