hellogles3 example: Fix start-up crash when using dynamic GL

Move the instantiation of QGuiApplication to the top since it is
required by QOpenGLContext::openGLModuleType().

Task-number: QTBUG-55671
Change-Id: I506cee193fe2ba48400851588a8ef079848bc2f4
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

examples/opengl/hellogles3/main.cpp

@@ -64,6 +64,8 @@
 
 int main(int argc, char *argv[])
 {
+    QGuiApplication app(argc, argv);
+
     QSurfaceFormat fmt;
     fmt.setDepthBufferSize(24);
 
@@ -79,8 +81,6 @@ int main(int argc, char *argv[])
 
     QSurfaceFormat::setDefaultFormat(fmt);
 
-    QGuiApplication app(argc, argv);
-
     GLWindow glWindow;
     glWindow.showMaximized();