Start new block after loop free

In the attached test case we ended up not updating a leftover
MATCH jump in the unreachable_free block. There's different ways
this can be addressed,

Start new block after loop free

In the attached test case we ended up not updating a leftover
MATCH jump in the unreachable_free block. There's different ways
this can be addressed, but in this case we can just make sure that
a new block is started after the loop free, which will allow it
to be dropped as unreachable. We only need to retain the free
itself for live-range reconstruction.

Fixes oss-fuzz #39516.

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