Fix dropping a range of stashes in filtered mode

To fix the problem described in the previous commit, iterate backwards over the
stashes that we want to delete. This allows us to use their Index field.

pkg/gui/controllers/stash_controller.go

@@ -161,9 +161,8 @@ func (self *StashController) handleStashDrop(stashEntries []*models.StashEntry)
 		Prompt: self.c.Tr.SureDropStashEntry,
 		HandleConfirm: func() error {
 			self.c.LogAction(self.c.Tr.Actions.Stash)
-			startIndex := stashEntries[0].Index
-			for range stashEntries {
-				err := self.c.Git().Stash.Drop(startIndex)
+			for i := len(stashEntries) - 1; i >= 0; i-- {
+				err := self.c.Git().Stash.Drop(stashEntries[i].Index)
 				self.c.Refresh(types.RefreshOptions{Scope: []types.RefreshableView{types.STASH}})
 				if err != nil {
 					return err

pkg/integration/tests/stash/drop_multiple_in_filtered_mode.go

@@ -58,24 +58,14 @@ var DropMultipleInFilteredMode = NewIntegrationTest(NewIntegrationTestArgs{
 					Content(Contains("Are you sure you want to drop the selected stash entry(ies)?")).
 					Confirm()
 			}).
-			/* EXPECTED:
 			IsEmpty()
-			ACTUAL: */
-			Lines(
-				Contains("stash two-a"),
-			)
 
 		t.GlobalPress(keys.Universal.Return) // cancel filtering mode
 		t.Views().Stash().
 			Lines(
-				/* EXPECTED:
 				Contains("stash four"),
 				Contains("stash three"),
 				Contains("stash one"),
-				ACTUAL: */
-				Contains("stash four"),
-				Contains("stash two-a"),
-				Contains("stash one"),
 			)
 	},
 })