idlwave-concatenate-rinfo-lists fix

* progmodes/idlwave.el (idlwave-concatenate-rinfo-lists):
Handle idlwave-last-system-routine-info-cons-cell being nil.

This seems to prevent an error on typing `C-c TAB',
idlwave-update-routine-info, in an idlwave buffer.

2 files changed, 11 insertions, 5 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 219e3d902ea..3fa1ffe40a7 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -8,6 +8,9 @@
 
 2013-05-29  Glenn Morris  <rgm@gnu.org>
 
+        * progmodes/idlwave.el (idlwave-concatenate-rinfo-lists):
+        Handle idlwave-last-system-routine-info-cons-cell being nil.
+
         * progmodes/idlwave.el (idlwave-scan-user-lib-files)
         (idlwave-write-paths): Simplify via with-temp-buffer.
 
diff --git a/lisp/progmodes/idlwave.el b/lisp/progmodes/idlwave.el
index cbcd2f9d10e..ba9a632b949 100644
--- a/lisp/progmodes/idlwave.el
+++ b/lisp/progmodes/idlwave.el
@@ -5078,11 +5078,14 @@ Cache to disk for quick recovery."
   ;; The sequence here is important because earlier definitions shadow
   ;; later ones.  We assume that if things in the buffers are newer
   ;; then in the shell of the system, they are meant to be different.
-  (setcdr idlwave-last-system-routine-info-cons-cell
-          (append idlwave-buffer-routines
-                  idlwave-compiled-routines
-                  idlwave-library-catalog-routines
-                  idlwave-user-catalog-routines))
+  (let ((temp (append idlwave-buffer-routines
+                      idlwave-compiled-routines
+                      idlwave-library-catalog-routines
+                      idlwave-user-catalog-routines)))
+    ;; Not actually used for anything?
+    (if idlwave-last-system-routine-info-cons-cell
+        (setcdr idlwave-last-system-routine-info-cons-cell temp)
+      (setq idlwave-last-system-routine-info-cons-cell (cons temp nil))))
   (setq idlwave-class-alist nil)
 
   ;; Give a message with information about the number of routines we have.