Gnus: Fix edge cases with no data being returned and Courier eccentricity.

* lisp/gnus/nnimap.el (nnimap-retrieve-headers-progress): Handle edge
  case where `headers' is nil.  This can occur if the IMAP server does
  not have permissions to read messages from a folder, but can write new
  messages to the folder.
  (nnimap-request-article-part): Do not insert `data' if it is nil.

* lisp/net/imap.el (imap-parse-fetch): Courier can insert spurious blank
  characters which will confuse `read', so skip past them.

2 files changed, 8 insertions, 5 deletions

diff --git a/lisp/gnus/nnimap.el b/lisp/gnus/nnimap.el
index e0bb5ad48f2..a38d35444a3 100644
--- a/lisp/gnus/nnimap.el
+++ b/lisp/gnus/nnimap.el
@@ -620,7 +620,7 @@ If EXAMINE is non-nil the group is selected read-only."
        ;; to make it more clear.
        (mm-with-unibyte-buffer
          (buffer-disable-undo)
-         (insert headers)
+         (when headers (insert headers))
          (let ((head (nnheader-parse-naked-head uid)))
            (mail-header-set-number head uid)
            (mail-header-set-chars head chars)
@@ -950,9 +950,10 @@ function is generally only called when Gnus is shutting down."
               (erase-buffer)
               (let ((data (imap-fetch article part prop nil
                                       nnimap-server-buffer)))
-                (insert (nnimap-demule (if detail
-                                           (nth 2 (car data))
-                                         data))))
+                (when data
+                  (insert (nnimap-demule (if detail
+                                             (nth 2 (car data))
+                                           data)))))
               (nnheader-ms-strip-cr)
               (gnus-message
                10 "nnimap: Fetching (part of) article %d from %s...done"
diff --git a/lisp/net/imap.el b/lisp/net/imap.el
index 6726bfda200..85afffc100b 100644
--- a/lisp/net/imap.el
+++ b/lisp/net/imap.el
@@ -2493,7 +2493,9 @@ Return nil if no complete line has arrived."
   (when (eq (char-after) ?\()
     (let (uid flags envelope internaldate rfc822 rfc822header rfc822text
               rfc822size body bodydetail bodystructure flags-empty)
-      (while (not (eq (char-after) ?\)))
+      (while (let ((moved (skip-chars-forward " \t")))
+               (prog1 (not (eq (char-after) ?\)))
+                 (unless (= moved 0) (backward-char))))
         (imap-forward)
         (let ((token (read (current-buffer))))
           (imap-forward)