fix: let the upload run when no board is selected

[kittaakos]

Motivation

IDE2 must not disable the upload from the UI when no board is selected. Otherwise, IDE2 does not receive the no FQBN error from the CLI and cannot suggest selecting a board via the Tools > Board menu.

Change description

Other information

Closes arduino/arduino-ide#1714

Reviewer checklist

• [ ] PR addresses a single concern.
• [ ] The PR has no duplicates (please search among the Pull Requests before creating one)
• [ ] PR title and description are properly filled.
• [ ] Docs have been added / updated (for bug fixes / features)

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