[Clang] Fix a crash when trying to initialize an invalid aggregate.

We did not return an error when failing to producing
a valid expression when performing the initialization of
an aggregate initialized with a parenthesized list of expressions.

This is a regression introduced in Clang 17.

Fixes #63278

Reviewed By: aaron.ballman, #clang-language-wg

Differential Revision: https://reviews.llvm.org/D154486