[tracker] tracker-extract: Fix possible invalid memory read/write

[Carlos Garnacho <carlosg src gnome org>]

commit ee7b08f0c4853a2a88488c0accccb6413302876e
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Nov 30 12:39:06 2014 +0100

    tracker-extract: Fix possible invalid memory read/write
    
    If length is 0, out of bounds data would be read, and then written.

 src/libtracker-extract/tracker-utils.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/libtracker-extract/tracker-utils.c b/src/libtracker-extract/tracker-utils.c
index 92a0549..308fb5d 100644
--- a/src/libtracker-extract/tracker-utils.c
+++ b/src/libtracker-extract/tracker-utils.c
@@ -936,7 +936,7 @@ tracker_keywords_parse (GPtrArray   *store,
        }
 
        len = strlen (keywords_d);
-       if (keywords_d[len - 1] == '"') {
+       if (len > 0 && keywords_d[len - 1] == '"') {
                keywords_d[len - 1] = '\0';
        }