1.19 fix null pointers when strengthening unknown mobs

[andrei-pham]

Hello @Globox1997!

Just adding a small guard against accessing the default attributes, since it's sometimes crashing when encountering mobs of unknown types (such as those added by other mods), after the latest update.

Let me know what you think

[Globox1997]

Hi arpds, this looks great, thanks for your work :)