fix: Update defaultParcelSize only when it exists

[Manizuca]

Signed-off-by: Matias Zuniga [email protected]

Resolves reactioncommerce/reaction#6257
Impact: minor
Type: bugfix

Issue

On a clean install, the Base of Unit Measure or Base Unit of Length cannot be changed unless the Default Parcel Size value is set.
This happens because the code tries to update defaultParcelSize, even if it doesn't exist, throwing TypeError: Cannot read property 'weight' of null when trying to calculate the new defaultParcelSize.

Solution

Check for the existence of defaultParcelSize before trying to calculate an updated value.

Testing

1. Start a fresh setup with this PR applied.
2. Login as admin user
3. Try and change Base of Unit Measure or Base Unit of Length
4. baseUOM or baseUOL was updated without errors.

[Manizuca]

The eslint failure is unrelated to this PR

[manueldelreal]

After #290 is merged the eslint error will go away. I didn't see the error with this one, want to confirm locally as well @willopez ?

[willopez]

@manueldelreal you correct, that eslint error will go away once #290 is merged.

[willopez]

@Manizuca Thank you for your contribution. The eslint error will go away if you rebase using the latest upstream trunk.

[willopez]

Thanks!for fixing this @Manizuca

[willopez]

LGTM