[Bug c++/89217] [9 Regression] ICE tree check: expected constructor, have error_mark in split_nonconstant_init_1

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89217

--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
...which means that we should most likely deal with REFERENCE_REF_P in case
COMPONENT_REF in tsubst_copy_and_build.  Testing a patch.