Compile Warnings

[BudDavis]

/home/bdavis/jsbsimedit/src/MainWindow/ExampleTab.cpp: In constructor ‘JSBEdit::ExampleTab::ExampleTab(Glib::RefPtrGtk::Application&, const std::string&)’:
/home/bdavis/jsbsimedit/src/MainWindow/ExampleTab.cpp:6:62: warning: unused parameter ‘app’ [-Wunused-parameter]
6 | ExampleTab::ExampleTab(const Glib::RefPtrGtk::Application& app
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
[ 22%] Building CXX object CMakeFiles/JSBSimEdit.dir/src/MainWindow/ExampleWindow.cpp.o
/home/bdavis/jsbsimedit/src/MainWindow/ExampleWindow.cpp: In member function ‘bool JSBEdit::ExampleWindow::load_stack(Glib::RefPtrGtk::Application&)’:
/home/bdavis/jsbsimedit/src/MainWindow/ExampleWindow.cpp:162:70: warning: unused parameter ‘app’ [-Wunused-parameter]
162 | bool ExampleWindow::load_stack(const Glib::RefPtrGtk::Application &app) //tabs
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
[ 23%] Building CXX object CMakeFiles/JSBSimEdit.dir/src/MainWindow/MainWindow.cpp.o
In file included from /home/bdavis/jsbsimedit/src/MainWindow/MainWindow.cpp:1:
/home/bdavis/jsbsimedit/src/MainWindow/MainWindow.hpp: In constructor ‘MainWindow::MainWindow()’:
/home/bdavis/jsbsimedit/src/MainWindow/MainWindow.hpp:21:19: warning: unused variable ‘jsbsim_content’ [-Wunused-variable]
21 | Gtk::Box* jsbsim_content = create_example_jsbsim_box();
| ^~~~~~~~~~~~~~

[Bplav18]

the unused parameter app has been fixed by returning a void in both, Window.cpp and ExampleTab.cpp..