[Bug] convert mobi to epub suddenly exit

[polyproline]

Cpus:
        8
Platform:
        win32
Computer:
        uname_result(system='Windows', node='***', release='10', version='10.0.19045', machine='AMD64')
Python_impl:
        CPython
Python version:
        3.10.1 (main, Dec 23 2021, 12:15:59) [MSC v.1929 64 bit (AMD64)]
Calibre version:
        6.18.1

> ebook-convet test.mobi test.epub

It suddenly exit.
I use calibre-debug and CALIBRE_DEVELOP_FROM, reproduce this problem, and print the flame.
calibre\ebooks\conversion\plumber.py(1108)run()
calibre\customize\conversion.py(242)__call__()
calibre\ebooks\conversion\plugins\mobi_input.py(30)convert()
calibre\ebooks\mobi\reader\mobi6.py(167)extract_content()
calibre\ebooks\mobi\reader\mobi6.py(830)extract_text()
calibre\ebooks\compression\palmdoc.py(13)decompress_doc()

I belive it happened in calibre\ebooks\compression\palmdoc.c:cpalmdoc_decompress.

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.