LibGUI: Focus next tab after closing active tab

Focus the next tab after closing the currently active tab.
If the tab being closed is the last one then the new last
tab is active.

Userland/Libraries/LibGUI/TabWidget.cpp

@@ -56,10 +56,17 @@ void TabWidget::add_widget(const StringView& title, Widget& widget)
 void TabWidget::remove_widget(Widget& widget)
 {
     VERIFY(widget.parent() == this);
-    if (active_widget() == &widget)
-        activate_next_tab();
-    m_tabs.remove_first_matching([&widget](auto& entry) { return &widget == entry.widget; });
+    auto tab_index = m_tabs.find_if([&widget](auto& entry) { return &widget == entry.widget; }).index();
+
+    auto is_active = active_widget() == &widget;
+    m_tabs.remove(tab_index);
     remove_child(widget);
+
+    if (is_active && m_tabs.size() > 0) {
+        auto next_tab_index = tab_index >= m_tabs.size() ? m_tabs.size() - 1 : tab_index;
+        set_tab_index(next_tab_index);
+    }
+
     update_focus_policy();
     if (on_tab_count_change)
         on_tab_count_change(m_tabs.size());