mesa: add missing error-path
The ARB_shader_objects spec says the following:
The error INVALID_VALUE is generated by any command that takes one or more handles as input, and one or more of these handles are not an object handle generated by OpenGL.
And a long, long time ago, we used do to just that for glDeleteObjectARB... Until 9ac9605d, all the way back in February 2006, where the error condition was removed without explanation.
Let's restore it, because it should really be there.
This was noticed by running the tests that are in the mesa-demos repository, that actually tested this condition.
Cc: mesa-stable