Unclean install and uninstall of mzscheme when PLT web server is selected

When installing mzscheme, there is an option to activate the PLT web server. When this option is not selected, mzscheme installs cleanly and can be cleanly uninstalled again (when slib is not installed - see bug #38936). When the option is selected, installation produces this error:

E: mzscheme: subprocess post-installation script returned error exit status 1

and the following details (these have been copied by hand, so apologies for any errors):

unpacking mzscheme (from .../mzscheme_1%3a352-1_i386.deb) ...
Setting up mzscheme (352-1) ...

Starting web server: mzserver ... start-stop-daemon: stat /usr/lib/plt/bin/mzscheme: No such file or directory (No such file or directory)
failed
invoke-rc.d: initscript mzscheme, action "start" failed.
dpkg: error processing mzscheme (--configure):
 subprocess post-installation script returned error exit status 1
Errors were encountered while processing:
 mzscheme
E: Sub-process /usr/bin/dpkg returned an error code (1)
A package failed to install. Trying to recover:
Setting up mzscheme (352-1) ...

Starting web server: mzserver ... start-stop-daemon: stat /usr/lib/plt/bin/mzscheme: No such file or directory (No such file or directory)
failed
invoke-rc.d: initscript mzscheme, action "start" failed.
dpkg: error processing mzscheme (--configure):
 subprocess post-installation script returned error exit status 1
Errors were encountered while processing:
 mzscheme

Similarly, if the webserver option was selected at install, uninstall produces this error message:

E: mzscheme: subprocess pre-removal script returned error exit status 1

and these details (again hand-copied):

(Reading database ... 125335 files and directories currently installed.)
Removing mzscheme ...

Stopping web server: mzserver ... start-stop-daemon: stat /usr/lib/plt/bin/mzscheme: No such file or directory (No such file or directory)
failed
invoke-rc.d: initscript mzscheme, action "stop" failed.
dpkg: error processing mzscheme (--remove):
 subprocess pre-removal script returned error exit status 1
dpkg: error while cleaning up:
 subprocess post-installation script returned error exit status 1
Errors were encountered while processing:
 mzscheme
E: Sub-process /usr/bin/dpkg returned an error code (1)
A package failed to install. Trying to recover:

As a workaround, manually creating a symlink from /usr/lib/plt/bin/mzscheme to /usr/bin/mzscheme allows an apparently clean install and uninstall. (And the PLT web server seems to work once installed.)