Bug

In mergeIcons (bin/helpers/merge.ts), the custom system tray icon handling has two defects:

await fsExtra.pathExists(options.systemTrayIcon);   // result discarded (dead)
const iconExt = path.extname(options.systemTrayIcon).toLowerCase();
if (iconExt === '.png' || iconExt === '.ico') {
  const trayIcoPath = path.join(npmDirectory, `src-tauri/png/${safeAppName}${iconExt}`);
  trayIconPath = `png/${safeAppName}${iconExt}`;   // assigned BEFORE the copy
  await fsExtra.copy(options.systemTrayIcon, trayIcoPath);
}
...
} catch (err) {
  logger.warn(`✼ ...`);
  logger.warn(`✼ Default system tray icon will remain unchanged.`);   // but it already changed
}

1. Dead check — await fsExtra.pathExists(...) is awaited but its boolean result is never used.
2. Premature assignment — trayIconPath (which becomes system_tray_path in the config) is set before fsExtra.copy. If the source is missing or the copy throws, the catch warns that the default "will remain unchanged", but the config already points at png/<name>.<ext> — a file that was never written. The app then references a non-existent tray icon.

Fix

Use the existence check to keep the default (with a clear "not found" message), and assign trayIconPath only after a successful copy. PR attached.