Add missing symbol

Strangely enough, this wasn't flagged when running `pnpm begood` locally.
CI found it though, and it's definitely a real issue.
It's unclear to me how that's possible.

Author: Byron

apps/desktop/src/components/BranchesViewPR.svelte

@@ -26,6 +26,7 @@
 	const forge = inject(DEFAULT_FORGE_FACTORY);
 	const prService = $derived(forge.current.prService);
 	const prQuery = $derived(prService?.get(prNumber, { forceRefetch: true }));
+	const prUnit = $derived(prService?.unit);
 
 	const uiState = inject(UI_STATE);
 	const projectState = $derived(uiState.project(projectId));