Panic in `mailparse`

[link2xt]

The error is Abort message: 'assertion failed: ix_start < line.len()' in the log https://support.delta.chat/t/qq-email-account-encountered-a-crash/3599/2

The crash is this line:
https://github.com/staktrace/mailparse/blob/d6494b98a8d0baf14a4574c7a8f642a66d7674e6/src/lib.rs#L123

In the core itself we have eliminated most of the indexing/slicing and don't introduce more: #6214

I file the issue here because we need to fix the bug in mailparse, update it an have a test in the core reproducing the crash. Upstream mailparse issue staktrace/mailparse#130
Upstream fix PR is at staktrace/mailparse#131

Core version in the log is 1.155.5. It uses mailparse 0.16.0 in Cargo.lock.

[link2xt]

With #6583 fixes to get our fuzzer setup working again I managed to reproduce a crash by using cargo bolero test fuzz_mailparse --release=false -s NONE. I had to do cp ../test-data/message/* fuzz_targets/corpus/ to give the fuzzer something to start with that looks like emails and not some random search and it produced this:

Return-Path: <37u6sZRoKALMghkXier-lfmi-mel-kXihkmbgZZhhZeX.Vhf@smtp-tls-reporting.bounces.google.com>
Delivered-To: root@nine.testrun.org
ls-report-submitter:tls-report-domain
         :date:mime-version:from:to:cc:subject:date:message-id:reply-to;
        bh=ij33gq0ofQz4EhX9TLi6EGnOILUSDSZtwZir1iybY6o=;
        b=IQ/TiJ4wMppgECWZQaC8EE3Q3ON4VjB94gp/l4uxL0mSAKo+CeKn+wh5jJooKCN3uZ
         wjp9w3+fcQq/3UvvthDzlcBHA2QHXkGC4ONliODX4uaWalRkc21ODHVvx8ILGuAFeKxw
         dl6+hn3Qk56FbVdRNBrAKvx7YvJjQHecrO79AoURhcCVfNtqpwPXuok4c/w6TtLhLLsu
         pwcPlkAJphdD5hvXLciHjRszvIWn.org
Content-Type: multipart/digestmultipart/report; boundary="000000000000cc153d060f720056"; report-type=tlsrpt

--00000 000000cc153d060f720056
Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes

This is an aggregate TLS report from google.com

--000000000001cc153d060f720056
Content-Type: application/tlsrpt+gzip;
	name="google.com!nine.testrun.org!1705708800!1705795199!001.json.gz"
Content-Disposition: attachment;
	filename="google.~com!nine.testrun.org!1705708800!1705795199!001.json.gz"
Contenttls-report-domain
         :date:mime-version:from:to:cc:subject:date:message-id:reply-to;
        bh=ij33gq0ofQz4EhX9TLi6EGnOILUSDSZtwZir1iybY6o=;
        b=IQ/TiJ4wMppgECWZQaC8EE3Q3ON4VjB94gp/l4uxL0mSAKo+CeKn+wh5jJooKCN3uZ
         wjp9w3+fcQq/3UvYym7C6agN
PkBW9v16Cy7TIjdP86Wb5sucf6AXLWxRFrw6Q8pyGFtsd9vzUhCRarAFyLTJwxQPtrijGd1wdI0g
q9VyXRmjDr/Na4ouoEjeow36gzJPyv+qB7lW7mN0aR6fiV2rc+895HzqxZV3+kNPPUqHl8U35ORC
2yf4WzfjeBi/APFqfhD/AQAA
--000000000000cc153d060f720056--

As an attachment:
crash.txt

Now I need to turn this into a testcase, minify and figure out how to fix the issue properly.

[link2xt]

The fix and small testcase is at staktrace/mailparse#131