Fixed bug where nil was stored as a scaled texture.

ui/textures.go

@@ -109,6 +109,9 @@ func (t *Textures) Scaled(texture Texture, scale float32) Texture {
 		}
 	}
 	scaled := ScaleTexture(t.render, texture, scale)
+	if scaled == nil {
+		return nil
+	}
 	textures[scale] = scaled
 	t.scaled[texture] = textures
 	return scaled