getTruncateExpr may not always return a SCEVAddRecExpr when truncating
loop bounds. Add a check to verify the result type before casting, and
bail out of the transformation if the cast would be invalid.
This prevents potential crashes from invalid casts when dealing with
complex loop bounds.
Co-authored by Michael Rowan
Resolves [#153090](https://github.com/llvm/llvm-project/issues/153090)
4f551b55ae