Examples: Fix crash/high CPU usage when minimized

examples/GraphicsTest/main.cpp

@@ -6,7 +6,9 @@
 #include <NZSL/SpirvPrinter.hpp>
 #include <Nazara/Utility.hpp>
 #include <array>
+#include <chrono>
 #include <iostream>
+#include <thread>
 
 int main()
 {
@@ -215,7 +217,10 @@ int main()
 
 		Nz::RenderFrame frame = window.AcquireFrame();
 		if (!frame)
+		{
+			std::this_thread::sleep_for(std::chrono::milliseconds(1));
 			continue;
+		}
 
 		viewerInstance.UpdateViewMatrix(Nz::Matrix4f::TransformInverse(viewerPos, camAngles));
 		viewerInstance.UpdateEyePosition(viewerPos);