Extra quote in format statement causes odd behaviour

[technoblogy]

For example:

> (format t "~5,''0g" 3.14158)
'''''''''''''''''''''''''''''''''''''''''''3.14158
nil

Should give something like:

> (format t "~5,''0g" 3.14158)

  "~5,''0g"
        ^
Error: 'format' command '~0' not valid