[clang][ItaniumMangle] Check SizeExpr for DependentSizedArrayType
(PR49478)
As ArrayType::ArrayType mentioned in clang/lib/AST/Type.cpp, a
DependentSizedArrayType might not have size expression because it it
used as the type of a dependent array of unknown bound with a dependent
braced initializer.
Thus, I add a check when mangling array of that type.
This should fix https://bugs.llvm.org/show_bug.cgi?id=49478
Reviewed By: Richard Smith - zygoloid
Differential Revision: https://reviews.llvm.org/D99407