Avoid segfaults in Rmail-MIME

Rmail-MIME decodes text of email, including removal of
CR characters, but that can segfault if the text of some
MIME part is empty.
* src/coding.c (decode_coding_raw_text):
* lisp/mail/rmailmm.el (rmail-mime-insert-decoded-text): Don't
attempt to decode empty text region.

1 files changed, 3 insertions, 1 deletions

diff --git a/src/coding.c b/src/coding.c
index b21ed360578..5591b7fed45 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -5270,7 +5270,9 @@ decode_coding_raw_text (struct coding_system *coding)
   coding->chars_at_source = 1;
   coding->consumed_char = coding->src_chars;
   coding->consumed = coding->src_bytes;
-  if (eol_dos && coding->source[coding->src_bytes - 1] == '\r')
+  if (eol_dos
+      && coding->src_bytes > 0  /* empty source text? */
+      && coding->source[coding->src_bytes - 1] == '\r')
     {
       coding->consumed_char--;
       coding->consumed--;