fix(frontend): default amount unit for empty protocols

[eatyourgreens]

Make sure the dosing compartments have a default unit set, even when there is no dosing information in an uploaded CSV. Otherwise, Trial Design doesn't let you choose a unit.

[sonarcloud[bot]]

Quality Gate passed for 'pkpdapp'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 76.41%. Comparing base (a4d1ade) to head (dd61cc9). Report is 1 commits behind head on development.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #493 +/- ## =============================================== - Coverage 76.41% 76.41% -0.01% =============================================== Files 108 108 Lines 5606 5609 +3 =============================================== + Hits 4284 4286 +2 - Misses 1322 1323 +1 ```

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[sonarcloud[bot]]

Quality Gate passed for 'pkpdapp-team_pkpdapp_frontend'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud