Incorrect error handling in shader compilation/linking

[ker2x]

While following your tutorial I ran into some issue and found out that the way you handle error is (apparently) not strictly correct. It seems that the best practice to check for error is the one in my change request.

I got this from https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/linkProgram and it works for me