Enforce a sane minimum window size and resolution

See: crash report #444

src/core/ArxGame.cpp

@@ -260,10 +260,18 @@ void ArxGame::setFullscreen(bool fullscreen) {
 			mode = GetWindow()->getDisplayModes().back();
 		}
 
+		// Clamp to a sane resolution!
+		mode.resolution.x = std::max(mode.resolution.x, s32(640));
+		mode.resolution.y = std::max(mode.resolution.y, s32(480));
+
 		GetWindow()->setFullscreenMode(mode.resolution, mode.depth);
 
 	} else {
 
+		// Clamp to a sane window size!
+		config.window.size.x = std::max(config.window.size.x, s32(640));
+		config.window.size.y = std::max(config.window.size.y, s32(480));
+
 		GetWindow()->setWindowSize(config.window.size);
 
 	}
@@ -309,6 +317,12 @@ bool ArxGame::initWindow(RenderWindow * window) {
 
 	}
 
+	// Clamp to a sane resolution and window size!
+	mode.resolution.x = std::max(mode.resolution.x, s32(640));
+	mode.resolution.y = std::max(mode.resolution.y, s32(480));
+	config.window.size.x = std::max(config.window.size.x, s32(640));
+	config.window.size.y = std::max(config.window.size.y, s32(480));
+
 	Vec2i size = config.video.fullscreen ? mode.resolution : config.window.size;
 
 	if(!m_MainWindow->init(version, size, config.video.fullscreen, mode.depth)) {
@@ -519,6 +533,8 @@ void ArxGame::OnWindowLostFocus(const Window &) {
 
 void ArxGame::OnResizeWindow(const Window & window) {
 
+	arx_assert(window.GetSize() != Vec2i::ZERO);
+
 	// A new window size will require a new backbuffer
 	// size, so the 3D structures must be changed accordingly.
 	wasResized = true;