My game character is unable to log in.

When attempting to log in, the following prompt appears:
Fatal error in Metadata/Monsters/PorcupineAnt/PorcupineAntLarge@28:
Number of shared states is different on client and server! Delta: 83
My character name is: KhoraUmbra
My computer has no MODs, plugins, or other mods installed, and I have not made any modifications to the game files in any form.