Fix DFU flash: ensure cleanup callback runs on USB error

[sensei-hacker]

User description

Problem

After DFU flashing completes successfully, users cannot reconnect to the flight controller without restarting the configurator.

Root Cause

In stm32usbdfu.js, when the final USB controlTransfer fails (expected when device reboots after successful flash), the error handler logs the error but doesn't call the callback. This leaves GUI.connect_lock = true, preventing reconnection.

Solution

Call the callback with an error code even when USB transfer fails, ensuring cleanup() runs and GUI.connect_lock gets cleared.

Testing

• Flashed firmware via DFU successfully
• Verified reconnection works immediately after flash without restarting configurator
• No regressions in DFU flashing behavior

Files Changed

• js/protocols/stm32usbdfu.js (+2 lines)

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PR Type

Enhancement, Bug fix, Tests, Documentation