bash crashes on command substitution

[Yuri]

On FreeBSD, I have this command line (1). When I move cursor right after 
'tmp', press <backspace> and <Tab>, it turns into (2)!
What happened?
The problem is completely reproducible.

bash-4.3.33

Yuri



--- (1) begin with this---
[root@yuri /usr/local/etc/rc.d]# [ "$(procstat $(cat /var/tmp/tor.pid)" ]

--- (2) result is this! ---
[root@yuri /usr/local/etc/rc.d]# [ "$(procstat $(cat /var/tmbash: 
command substitution: line 30: unexpected EOF while looking for matching `"'
bash: command substitution: line 31: syntax error: unexpected end of file
bash: command substitution: line 30: unexpected EOF while looking for 
matching `"'
bash: command substitution: line 31: syntax error: unexpected end of file
bash: command substitution: line 30: unexpected EOF while looking for 
matching `)'
bash: command substitution: line 31: syntax error: unexpected end of file
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