D&D5e - Question about something on a player's character sheet

I came across this mention of NaN on a player's character sheet when he rolls for Spiritual Weapon. You can see it on the screenshot above on the entry for the Spiritual Weapon and where he rolled it. I double checked that it came straight from the Compendium and it did. What is it, and is it right? My player is suspicious.

NaN stands for Not a Number. It's an error code in javascript. It means something has gone wrong on the sheet when calculating a value.

Ah, OK. What should I do about it? Does it mean there's something wrong with the compendium?

Hi Lexin! There is probably an out-of-gamut value in one of the fields required to generate the to-hit roll. Perhaps a space or text value in the Spellcasting score or part of the formula that creates it. It could be a malformed magic item, for instance. After casting the spell, press the up arrow in the chat input box. It should show you the formula that was sent (depending on how it was activated), and that might give you a clue where to look.

One thing you can do is edit the Spiritual Weapon attack, take a screenshot of that and post that. We might see what was broken. 

OK, not sure what this shows, but here it is:

Lexin said: OK, not sure what this shows, but here it is: Click on the spells tab and confirm that a spellcasting ability has been set: If not, click on the word "None" and change it to the appropriate stat. -Adam

Adam Caramon said: Click on the spells tab and confirm that a spellcasting ability has been set: You are correct, thank you. No spellcasting ability had been set for the character, and I've put that right now.

Lexin said: Adam Caramon said: Click on the spells tab and confirm that a spellcasting ability has been set: You are correct, thank you. No spellcasting ability had been set for the character, and I've put that right now. You're welcome.  Happy gaming. -Adam