bug#51489: emacs-shell-command+: 2.3.1 broken, fixed in 2.3.2

[Christopher Howard]

Hello, emacs-shell-command+ 2.3.1 is broken against Emacs 27.2, due to
a variable `shell-command-buffer-name` not necessarily being defined.
This problem is I believed fixed in 2.3.2 source which I see puts a
`bound-and-true-p` wrapper around the variable.

```
christopher@theoden ~$ neofetch --stdout
christopher@theoden 
------------------- 
OS: Guix System c6adc0947396daa6d85ab08837f9cbc86f4d8722 x86_64 
Host: OptiPlex 9020 00 
Kernel: 5.14.14-gnu 
Uptime: 2 days, 18 hours, 11 mins 
Packages: 91 (guix-system), 129 (guix-user) 
Shell: bash 5.0.16 
Resolution: 1920x1080 
DE: GNOME 
Theme: Adwaita [GTK2/3] 
Icons: Adwaita [GTK2/3] 
Terminal: .gnome-terminal 
CPU: Intel i5-4570 (4) @ 3.600GHz 
GPU: Intel HD Graphics 
GPU: AMD ATI Radeon HD 8490 / R5 235X OEM 
Memory: 4345MiB / 7869MiB 
```

-- 
Christopher Howard
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