Steps to reproduce :
_Open Minecraft and see the random splash text on the main menu
_Click "Options" then "Resouce Packs..."
_Replace your current resource pack(s) by another one with custom splashes included (or add it to the default ressource pack)
_Click "Done"
_Click "Done"
_See how the splash text from the previous resource(s) pack still shows up despite not belonging to the selected pack

Note : this issue might be related to MC-13118 since pressing Escape solves the issue.