re PR c++/71826 (ICE on valid C++ code with ambiguous member lookup: tree check: expected baselink, have error_mark in tsubst_baselink, at cp/pt.c:13737)

	PR c++/71826
	* pt.c (tsubst_baselink): Only set BASELINK_OPTYPE for BASELINK_P.

	* g++.dg/template/pr71826.C: New test.

From-SVN: r238441