Disable staging all files when there are none to stage

Besides the misleading error about submodules, the command crashes when
it runs before the first files refresh has come in: the file tree
doesn't exist yet at that point, and staging all of a tree that isn't
there dereferences a nil root node. That is easy to hit in a big repo,
where `git status` takes a moment while the panel sits there empty.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

pkg/gui/controllers/files_controller.go

@@ -130,10 +130,11 @@ func (self *FilesController) GetKeybindings(opts types.KeybindingsOpts) []*types
 			OpensMenu:   true,
 		},
 		{
-			Keys:        opts.GetKeys(opts.Config.Files.ToggleStagedAll),
-			Handler:     self.toggleStagedAll,
-			Description: self.c.Tr.ToggleStagedAll,
-			Tooltip:     self.c.Tr.ToggleStagedAllTooltip,
+			Keys:              opts.GetKeys(opts.Config.Files.ToggleStagedAll),
+			Handler:           self.toggleStagedAll,
+			GetDisabledReason: self.require(self.anyFilesDisplayed),
+			Description:       self.c.Tr.ToggleStagedAll,
+			Tooltip:           self.c.Tr.ToggleStagedAllTooltip,
 		},
 		{
 			Keys:              opts.GetKeys(opts.Config.Universal.GoInto),
@@ -916,6 +917,17 @@ func (self *FilesController) openSubmoduleConflictMenu(file *models.File) error
 	})
 }
 
+// The stage-all command acts on the file tree as it is displayed, so there has
+// to be something in it. This is also the case before the first files refresh
+// has come in, when there is no tree at all yet.
+func (self *FilesController) anyFilesDisplayed() *types.DisabledReason {
+	if self.context().FileTreeViewModel.Len() == 0 {
+		return &types.DisabledReason{Text: self.c.Tr.NoChangedFiles}
+	}
+
+	return nil
+}
+
 func (self *FilesController) toggleStagedAll() error {
 	if err := self.toggleStagedAllWithLock(); err != nil {
 		return err

pkg/integration/tests/file/stage_all_without_changed_files.go

@@ -19,10 +19,7 @@ var StageAllWithoutChangedFiles = NewIntegrationTest(NewIntegrationTestArgs{
 			IsEmpty().
 			Press(keys.Files.ToggleStagedAll).
 			Tap(func() {
-				/* EXPECTED:
 				t.ExpectToast(Contains("No changed files"))
-				ACTUAL: */
-				t.ExpectPopup().Alert().Title(Equals("Error")).Content(Contains("Nothing to stage")).Confirm()
 			})
 	},
 })