[gnome-shell] altTab: Fix a wrong variable name

[Florian Müllner <fmuellner src gnome org>]

commit c67460a1e3b9103cbcd1adf175c03f2cbc37b4a2
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Thu Jun 20 23:09:37 2019 +0200

    altTab: Fix a wrong variable name
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/587

 js/ui/altTab.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/js/ui/altTab.js b/js/ui/altTab.js
index 6c9aaf1c1..8b22afa2d 100644
--- a/js/ui/altTab.js
+++ b/js/ui/altTab.js
@@ -732,8 +732,8 @@ class AppSwitcher extends SwitcherPopup.SwitcherList {
 
         let iconPadding = themeNode.get_horizontal_padding();
         let iconBorder = themeNode.get_border_width(St.Side.LEFT) + 
themeNode.get_border_width(St.Side.RIGHT);
-        let [iconMinHeight, iconNaturalHeight] = this.icons[j].label.get_preferred_height(-1);
-        let iconSpacing = iconNaturalHeight + iconPadding + iconBorder;
+        let [, labelNaturalHeight] = this.icons[j].label.get_preferred_height(-1);
+        let iconSpacing = labelNaturalHeight + iconPadding + iconBorder;
         let totalSpacing = this._list.spacing * (this._items.length - 1);
 
         // We just assume the whole screen here due to weirdness happing with the passed width