Do you happen to have any stray copies of oolite-default-shader.vertex/.fragment in any of your OXP folders? eyeVector is supposed to always be defined and was used in the old lighting model too.
Edit: I think I can see what's happening. eyeVector is not defined if the NEED_EYEVECTOR macro in the shader is also not defined. For it to not be defined, the macros OOSTD_SPECULAR and OOSTD_NORMAL_AND_PARALLAX_MAP must both not be defined. Theoretically, a ship without any specular defaults could trigger this but I think default specular values are always applied. Will need to investigate because I can't get it to appear so far no matter what I disable. For now, a possible solution could be to move the #define OODIFFUSE_ORENNAYAR 1 line before the #define NEED_EYEVECTOR [...] one and change NEED_EYEVECTOR to