RPG Maker MV 'expParams'

TypeError
Cannot read property 'expParams' of undefined.

I assume this has to do with experience parameters. Maybe?

Here is what I did, and I may get scolded for it:
Actors have 2 items
From Classes to States are all grayed out.
Animations are left alone
Tilesets are left alone
Nothing in Common Events
System I removed all music and sound effects, vehicle images, removed the menu items. Bare Hands Thrust None is under [SV] Attack Motions
Types are all empty
Terms I removed all text except the four at the very bottom, and the first 6 under messages.

All that maybe overkill and totally not needed (hence the scolding), but I did it.

On the plus side, you can find gremlins hiding by going above and beyond the call of sanity like I did.

expparams has to do with calculating the corresponding XP based on the XP curve.
it's related to classes, so make a placeholder class and see if that solves the issue.

Any "undefined" error can only happen if something changed the engine, usually by adding plugins.
However if this means what I think
then you messed up here.

There are some parts of the database that are hardcoded into the engine - skills #1 and #2 (attack and guard) as well as state #1 (death) are the most important parts, that is why they get notes even if you start a new project.
If you remove those from the database then you'll get undefineds as soon as the engine needs them.

Similiar things can happen if you simply delete all terms-entries. The %s code in some of them is a placeholder, and if the engine tries to enter the value for those placeholders and doesn't find them (which means it no longer knows where to insert) you'll get errors as well.
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The database on a new project has values for a good reason: to allow you to playtest as soon as possible.
So you can make any part of the game you want and still playtest directly, while still allowing you to replace content AFTER YOU KNOW WHAT YOU NEED TO REPLACE IT WITH.
If you simply delete everything, then you are responsibe to place your version of the required data into it before you have any chance of testing your game.