mesa: Silence warning

Signed-off-by: Jakob Bornecrantz <jakob@vmware.com>
Reviewed-by Brian Paul <brianp@vmware.com>
Reviewed-by Ian Romanick <ian.d.romanick@intel.com>

src/mesa/program/nvvertparse.c

@@ -1424,6 +1424,7 @@ _mesa_parse_nv_vertex_program(struct gl_context *ctx, GLenum dstTarget,
 	 index = _mesa_add_state_reference(program->Base.Parameters,
 					   state_tokens);
 	 assert(index == i);
+	 (void)index;
       }
       program->Base.NumParameters = program->Base.Parameters->NumParameters;