fix: wrong check caused setting a new texture not to work if not yet loaded

[trusktr]

The missing .value was causing that conditional branch to never run, so trying to do the following wasn't working:

material.texture = new TextureLoader.load('foo.jpg') // does not wait for load, causes saveDimensions to result in [1,1]

Before this change it required a workaround:

new TextureLoader.load('foo.jpg', tex => {
  material.texture = tex // now it measures dimensions because the image is loaded
})

[marcofugaro]

oops, thank you!