Fix infinite loop on string offset during by-ref list assign

There is a deeper underlying issue here, in that the opcodes violate
VM write-fetch safety, but let's fix the infinite loop f

Fix infinite loop on string offset during by-ref list assign

There is a deeper underlying issue here, in that the opcodes violate
VM write-fetch safety, but let's fix the infinite loop first.

This fixes oss-fuzz #25352.

show more ...