Instantiate other mutexes by value

Like in the previous commit, this is preferred because the fields don't need to
be initialized this way.

pkg/gui/gui.go

@@ -118,7 +118,7 @@ type Gui struct {
 	// is being pushed). At the moment the rule is to use an item operation when
 	// we need to talk to the remote.
 	itemOperations      map[string]types.ItemOperation
-	itemOperationsMutex *deadlock.Mutex
+	itemOperationsMutex deadlock.Mutex
 
 	PrevLayout PrevLayout
 
@@ -684,8 +684,7 @@ func NewGui(
 		InitialDir:       initialDir,
 		afterLayoutFuncs: make(chan func() error, 1000),
 
-		itemOperations:      make(map[string]types.ItemOperation),
-		itemOperationsMutex: &deadlock.Mutex{},
+		itemOperations: make(map[string]types.ItemOperation),
 	}
 
 	gui.PopupHandler = popup.NewPopupHandler(