bug#10007: 24.0.50; wrong-type-argument stringp nil in *Occur*

[Drew Adams]

emacs -Q
 
C-x d some-directory
 
M-x occur
 
In the occur buffer:
 
C-x C-q
Move cursor to a date field and hit `w'.
You get an error saying that the Dired buffer is read-only.
 
That's true, but it's not clear that this is the most helpful message at
this point.
 
Now kill the Dired buffer.  Then move the cursor to a date field in the
occur buffer and hit `w'.  You get this error, which is definitely not
the right error message here:
 
self-insert-command: Wrong type argument: stringp, nil


In GNU Emacs 24.0.50.1 (i386-mingw-nt5.1.2600)
 of 2011-09-05 on 3249CTO
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.5) --no-opt'