proof script not displayed after startup

[coquser]

(I'm Dan Grayson <dan@…>)

I'm adapting pg under emacs to a new proof assistant that I'm writing (see ​https://github.com/DanGrayson/checker), and have just gotten started. The first problem was that after pg started scripting my proof script, the proof script buffer would disappear about the same time the *goals* and *response* buffers were displayed. I tracked the problem down to the function proof-display-three-b receiving nil as its first argument (why, I don't know), and "fixed" it as in the attached patch (but then the *goals* buffer doesn't appear). Oops, no, your tracker gives a weird error if I try to attach a file, so here is the diff:

diff --git a/generic/pg-response.el b/generic/pg-response.el
index 9f4b050..66e3205 100644
--- a/generic/pg-response.el
+++ b/generic/pg-response.el
@@ -157,7 +157,8 @@ Following POLICY, which can be one of 'smart, 'horizontal,
 (defun proof-display-three-b (&optional policy)
   "Layout three buffers in a single frame.  Only do this if buffers exist."
   (interactive)
-  (when (and (buffer-live-p proof-goals-buffer)
+  (when (and (buffer-live-p proof-script-buffer)
+	     (buffer-live-p proof-goals-buffer)
 	     (buffer-live-p proof-response-buffer))
     (save-excursion
       (proof-select-three-b