emojicompletion: Avoid a memory overrun

Don't read beyond the beginning of the string.

Fixes: #3245

diff --git a/gtk/gtkemojicompletion.c b/gtk/gtkemojicompletion.c
index 712418850a017a22998ad16f06d98e107c2b881d..31669c85d5adcec9a77988dfaa8cd5f3dae65252 100644 (file)
--- a/gtk/gtkemojicompletion.c
+++ b/gtk/gtkemojicompletion.c
@@ -115,7 +115,8 @@ next:
               break;
             }
         }
-      while (g_unichar_isalnum (g_utf8_get_char (p)) || *p == '_' || *p == ' ');
+      while (p > text &&
+             (g_unichar_isalnum (g_utf8_get_char (p)) || *p == '_' || *p == ' '));
 
       if (found_candidate)
         n_matches = populate_completion (completion, p, 0);