Fix SMP Mix single tree submission

[mgaseta]

Currently when trying to calculate values on step 5 or trying to submit the seedlot registration, the action return an error, as seen on the image below.

The expected behavior is that the submission and calculation would work without a problem for any valid parent tree (orchard or non-orchard) on the SMP Mix table.

Definition of done:

• Calculation working correctly
• Submission working correctly
• Tested and merged