Vault shares might become too big and cause overflow after many claims

[ben-kaufman]

After many claims from the vault, depositing might reach a situation where even a small deposit mints too many shares, causing an overflow either in the RewardController (on deposit), or even eventually in the deposit function itself.

The scenario may look like this, and will revert after 62 iterations:

it("Overflow", async () => {
    await setUpGlobalVars(accounts);

    for (let i = 0; i < 100; i++) {
      var staker = accounts[4];

      await stakingToken.approve(vault.address, web3.utils.toWei("1"), {
        from: staker,
      });

      await stakingToken.mint(staker, web3.utils.toWei("1"));

      console.log(i);

      await vault.deposit(web3.utils.toWei("1"), staker, { from: staker });

      assert.equal(await hatToken.balanceOf(staker), 0);
      await utils.increaseTime(7 * 24 * 3600);
      await advanceToSafetyPeriod();
      let tx = await vault.submitClaim(
        accounts[2],
        8000,
        "description hash",
        {
          from: accounts[1],
        }
      );

      let claimId = tx.logs[0].args._claimId;
      await utils.increaseTime(60 * 60 * 24);
      await vault.approveClaim(claimId, 8000);
    }
  });