Fix crash

examples/opengl/main.c

@@ -99,6 +99,11 @@ int main(int argc, char** argv)
 
 	struct lvrcInstance * compositor = lvrcCreateInstance(hmd);
 
+	if (!compositor)
+	{
+		return -1;
+	}
+
 	const int window_w = hmd_w/2;
 	const int window_h = hmd_h;