[clang] [AST][RecoveryExpr] Fix a crash on c89/c90 invalid InitListExpr (#88008) (PR #88014)

[Sam McCall via cfe-commits]

https://github.com/sam-mccall approved this pull request.

Thanks, this looks like the right fix, and cleaning up DclT while here makes sense.

https://github.com/llvm/llvm-project/pull/88014