Summary:
Default member initializers cannot refer to constructor parameters, but modernize-default-member-init was trying to when the default constructor had default arguments.
Change the check to ignore default arguments to the default constructor.
Fixes PR31524.
Reviewers: alexfh, aaron.ballman
Subscribers: cfe-commits, JDevlieghere, Eugene.Zelenko
Differential Revision: https://reviews.llvm.org/D28287
llvm-svn: 290972