[Extra checks are not needed for a zero API handle](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glDeleteProgram.xhtml "Description from the OpenGL reference") in [a function like “ComposedShader::set_loaded”](https://github.com/create3000/titania/blob/b555c2fea171fe2e0dadce9062a3c1d3ee33e92e/libtitania-x3d/Titania/X3D/Components/Shaders/ComposedShader.cpp#L145 "Update candidate").
