app/start: skip cleanup if shim is nil

Shim is created before any system operation happens.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

internal/app/start.go

@@ -154,6 +154,11 @@ func (a *app) Wait() (int, error) {
 	a.lock.Lock()
 	defer a.lock.Unlock()
 
+	if a.shim == nil {
+		fmsg.VPrintln("shim not initialised, skipping cleanup")
+		return 1, nil
+	}
+
 	var r int
 
 	if cmd := a.shim.Unwrap(); cmd == nil {