Code review comment for lp:~vanvugt/mir/fix-1271853

> should we be checking for errors after calling glUniformMatrix4fv() (it
> doesn't return an error code but the documentation seems to indicate there is
> one somewhere - we would presumably have seen GL_INVALID_OPERATION if we'd
> checked).

Seems a reasonable check, but I'll top approve in the meantime to get pixels back on our screens