[bugfix] Minor error in SeedFinalizeView if/else has_passphrase logic

[kdmukai]

Description

The current code's initial if branch has two errors, but important note: neither negatively affect the user. Despite being improperly pushed to the else branch, the outcome is the SAME in actual use.

Problem 1:

get_fingerprint is a function, not a property. It is correctly called with parentheses. The current python is (mistakenly) testing if the function itself (not its return value) equals a string, which is inherently always False.

Problem 2:

Even if get_fingerprint were a property, it would never equal the empty string.

It seems clear that the intention was instead to verify the expected state that the passphrase is empty when a seed is initially loaded (guaranteed to be the case in the main app; the else is only there for the unusual circumstance that the screenshot generator requires).

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Blame: I haven't checked the git history but this is almost definitely a bug I created. Mea culpa.

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Solution

Trivial fix to check the correct condition in the initial if.

Additional Information

This was discovered while testing on the esp32-P4's MicroPython port. Loading a new seed caused a ~0.5s delay before advancing to the next screen. That delay is not present on the Pi Zero.

While investigating, Claude found:

The current implementation re-derives the BIP-39 seed three times per seed load: once when the Seed is constructed at scan time, then twice more in the always-taken else branch (which strips and restores the passphrase, each set_passphrase() call triggering a fresh derivation).

BIP-39 derivation is a fixed 2048-round PBKDF2-HMAC-SHA512 — cheap against the Pi Zero's native library, but the dominant cost on the MicroPython target (ESP32-P4), where it becomes a visible post-scan pause. The fix takes the naked-seed path, deriving exactly once.

Measured on an ESP32-P4:

	Derivations	Seed-load time
Current	3×	~470 ms
Fixed	1×	~160 ms

A single derivation (~155 ms) is spec-mandated and irreducible; this change removes only the two redundant ones, cutting the pause by roughly two-thirds. No effect on the Pi Zero beyond eliminating wasted work.

Screenshots

n/a

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This pull request is categorized as a:

• Bug fix

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Checklist

I ran pytest locally

• All tests passed before submitting the PR

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I included screenshots of any new or modified screens

Should be part of the PR description above.

• N/A

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I added or updated tests

Any new or altered functionality should be covered in a unit test. Any new or updated sequences require FlowTests.

• N/A

Our existing FlowTests already cover this, but they couldn't detect the flaw in the if case because the outcome for the main app is successful through either if/else route. The only consequence is the noted performance churn on devices like the esp32-P4.

Confirmed that the screenshot generator still builds the SeedFinalizeView and SeedReviewPassphraseView screens as expected.

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I tested this PR hands-on on the following platform(s):

• Raspberry Pi OS Manual Build
• SeedSigner OS on a Pi0/Pi0W board
• Emulator

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