[tracker] tracker-extract-mp3: Fix segfault when trying to process NULL ID3 tag

[Martyn James Russell <mr src gnome org>]

commit d35800235ce93842f626b39b6925a0654c83c3dc
Author: Jonatan Pålsson <jonatan palsson pelagicore com>
Date:   Thu Jul 18 16:15:57 2013 +0100

    tracker-extract-mp3: Fix segfault when trying to process NULL ID3 tag
    
    When calling g_convert with a missing codepage, it returns NULL, while not
    setting an error (specifically, if the CP1252 code page is missing, a
    segmentation fault occurs). This means id3v24_text_to_utf8 and
    id3v2_text_to_utf8 may return NULL. If NULL is returned by these functions, do
    not process this tag further.

 src/tracker-extract/tracker-extract-mp3.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/src/tracker-extract/tracker-extract-mp3.c b/src/tracker-extract/tracker-extract-mp3.c
index 9b154f9..d5aea57 100644
--- a/src/tracker-extract/tracker-extract-mp3.c
+++ b/src/tracker-extract/tracker-extract-mp3.c
@@ -1292,6 +1292,9 @@ get_id3v24_tags (id3v24frame           frame,
                word = id3v24_text_to_utf8 (data[pos], &data[pos + 1], csize - 1, info);
                if (!tracker_is_empty_string (word)) {
                        g_strstrip (word);
+               } else {
+                       /* Can't do anything without word. */
+                       break;
                }
 
 #ifdef FRAME_ENABLE_TRACE
@@ -1480,8 +1483,12 @@ get_id3v23_tags (id3v24frame           frame,
 
                if (!tracker_is_empty_string (word)) {
                        g_strstrip (word);
+               } else {
+                       /* Can't do anything without word. */
+                       break;
                }
 
+
 #ifdef FRAME_ENABLE_TRACE
                g_debug ("ID3v2.3: Frame is %d, word is %s", frame, word);
 #endif /* FRAME_ENABLE_TRACE */
@@ -1625,6 +1632,9 @@ get_id3v20_tags (id3v2frame            frame,
                word = id3v2_text_to_utf8 (data[pos], &data[pos + 1], csize - 1, info);
                if (!tracker_is_empty_string (word)) {
                        g_strstrip (word);
+               } else {
+                       /* Can't do anything without word. */
+                       return;
                }
 
 #ifdef FRAME_ENABLE_TRACE