fix: don't free window twice

src/io/window.c

@@ -75,6 +75,11 @@ void window_close(void) {
 }
 
 void window_free(void) {
+	if (!win) {
+		debug("window has already been freed.");
+		return;
+	}
+
 	glfwDestroyWindow(win);
 	render_free();
 	win = NULL;

src/main.c

@@ -34,8 +34,8 @@ int main(int argc, char **argv) {
 		fatal("failed to initialise!");
 
 	window_loop();
-	window_free();
 
-	// return success, since some architectures do not follow 0=success
+	/* return success, since some architectures do not follow 0=success
+	 * This action will call `quit`. */
 	return EXIT_SUCCESS;
 }