As of current state of revised_text branch, it does no longer crash, but it spits :

<verbatim>
bll-mac:tk
% text .t
.t
% .t tag configure big -font {Helvetica -24}
{-background {} {} {} {}} {-bgstipple {} {} {} {}} {-borderwidth {} {} 0 {}} {-elide {} {} 0 {}} {-eolcolor {} {} {} {}} {-fgstipple {} {} {} {}} {-font {} {} {} {}} {-foreground {} {} {} {}} {-hyphencolor {} {} {} {}} {-hyphenrules {} {} {} {}} {-inactivebackground {} {} {} {}} {-inactiveforeground {} {} {} {}} {-inactiveselectbackground {} {} {} {}} {-inactiveselectforeground {} {} {} {}} {-indentbackground {} {} 0 {}} {-justify {} {} {} {}} {-lang {} {} {} {}} {-lmargin1 {} {} {} {}} {-lmargin2 {} {} {} {}} {-lmargincolor {} {} {} {}} {-offset {} {} {} {}} {-overstrike {} {} {} {}} {-overstrikecolor {} {} {} {}} {-overstrikefg -overstrikecolor} {-relief {} {} {} {}} {-rmargin {} {} {} {}} {-rmargincolor {} {} {} {}} {-selectbackground {} {} {} {}} {-selectforeground {} {} {} {}} {-spacing1 {} {} {} {}} {-spacing2 {} {} {} {}} {-spacing3 {} {} {} {}} {-tabs {} {} {} {}} {-tabstyle {} {} {} {}} {-underline {} {} {} {}} {-underlinecolor {} {} {} {}} {-underlinefg -underlinecolor} {-undo {} {} 1 1} {-wrap {} {} {} {}}
</verbatim>

That is: it apparently spits what would be the output of the configure command for a newly created tag, e.g.:
<verbatim>
  .t tag configure foobar
</verbatim>