HackStudio: Properly clear previous editor tabs when closing project

Before this commit the close tab button, which is meant to only
show when more than one tab is open, would be present on the tab
of a new project opened after the first project.

This was due to m_all_editor_tab_widgets not being cleared when closing
the first project. This is now cleared when close_current_project() is
called.

Userland/DevTools/HackStudio/HackStudioWidget.cpp

@@ -1543,8 +1543,9 @@ void HackStudioWidget::stop_debugger_if_running()
 void HackStudioWidget::close_current_project()
 {
     m_editors_splitter->remove_all_children();
-    add_new_editor_tab_widget(*m_editors_splitter);
+    m_all_editor_tab_widgets.clear();
     m_all_editor_wrappers.clear();
+    add_new_editor_tab_widget(*m_editors_splitter);
     m_open_files.clear();
     m_open_files_vector.clear();
     m_find_in_files_widget->reset();