[flang] Don't crash on bad inherited implied DO type (#91073)

Fortran has an ambiguously defined rule about the typing of index
variables of implied DO loops in DATA statements and array constructo

[flang] Don't crash on bad inherited implied DO type (#91073)

Fortran has an ambiguously defined rule about the typing of index
variables of implied DO loops in DATA statements and array constructors
that omit an explicit type specification. Such indices have the type
that they would have "if they were variables" in the innermost enclosing
scope. Although this could, and perhaps should, be read to mean that
implicit typing rules active in that innermost enclosing scope should be
applied, every other Fortran compiler interprets that language to mean
that if there is a type declaration for that name that is visible from
the enclosing scope, it is applied, and it is an error if that type is
not integer.

Fixes https://github.com/llvm/llvm-project/issues/91053.

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