Re: [Bug: 21.5-b28] Crash in VM piping message to nonexistent command

I get a reliable crash when piping a message in VM to a nonexistent Unix command using vm-pipe-message-to-command. Here's a gdb backtrace:

#0 0x90014ba8 in write () #1 0x00166720 in retry_write_1 (fildes=11, buf=0x2371800, nbyte=512, allow_quit=0) at sysdep.c:2755 #2 0x00106e50 in filedesc_writer (stream=0x20, data=0x2371800 ".21; 'needs': 0.24; 'url:%0': 0.27;\n\t\"don't\": 0.29; 'subject:] ': 0.31; 'across': 0.31;\n\t'header:MIME-version:1': 0.33; 'header:Message-id:1': 0.33;\n\t'supported': 0.33; 'still': 0.33; 'url:org': 0.33;"..., size=512) at lstream.c:1180 #3 0x00105cf8 in Lstream_really_write (lstr=0xedd560, data=0x2371800 ".21; 'needs': 0.24; 'url:%0': 0.27;\n\t\"don't\": 0.29; 'subject:] ': 0.31; 'across': 0.31;\n\t'header:MIME-version:1': 0.33; 'header:Message-id:1': 0.33;\n\t'supported': 0.33; 'still': 0.33; 'url:org': 0.33;"..., size=512) at lstream.c:380 #4 0x00108560 in Lstream_write_1 (lstr=0xedd560, data=0x2371400, size=512) at lstream.c:419 #5 0x00108620 in Lstream_write (lstr=0xedd560, data=0x2371400, size=512) at lstream.c:602 #6 0x0008ce8c in coding_writer (stream=0x20, data=0x2371800 ".21; 'needs': 0.24; 'url:%0': 0.27;\n\t\"don't\": 0.29; 'subject:] ': 0.31; 'across': 0.31;\n\t'header:MIME-version:1': 0.33; 'header:Message-id:1': 0.33;\n\t'supported': 0.33; 'still': 0.33; 'url:org': 0.33;"..., size=0) at file-coding.c:1888 #7 0x00105cf8 in Lstream_really_write (lstr=0xedaea0, data=0x223f600 "'url-ip:194/8': 0.36;\n\t'skip:_ 40': 0.37; 'received:208.210.124.72': 0.37;\n\t'received:snug.pobox.com': 0.37; 'received:194.109.24.22': 0.37;\n\t'received:smtp-vbr2.xs4all.nl': 0.37; 'charset:us-ascii': "..., size=512) at lstream.c:380 #8 0x00107e84 in Lstream_close (lstr=0xedaea0) at lstream.c:419 #9 0x00116c54 in deactivate_process (process=15586400) at process.c:2136 #10 0x00118338 in status_notify () at process.c:2170 #11 0x000696a4 in Faccept_process_output (process=2320080, timeout_secs=37165056, timeout_msecs=27) at event-stream.c:2732 #12 0x0011a7f0 in unix_send_process (proc=15586400, lstream=0xedd670) at process-unix.c:1554