I created the texture in GIMP, so I went back into GIMP. Now that I'm noticing, GIMP uses an Alpha Channel by default which cannot be deleted. The Alpha was solid white, so that shouldn't be the problem. However, I then opened the texture in Photoshop to delete the Alpha Channel, and it wasn't there. The Alpha Channel must just be a GIMP thing. Since the texture doesn't have an existing Alpha Channel after all, Alpha isn't an issue.