commit 788af4df46147bce18f929ce79f93e619207978f
Author: Todd Fiala <tfiala@google.com>
Date:   Fri Feb 14 13:57:27 2014 -0800

    Guard against Python readline module NULL dereference.
    
    This fixes the following bug in lldb:
    http://llvm.org/bugs/show_bug.cgi?id=18841

diff --git a/Modules/readline.c b/Modules/readline.c
index 0b043ae..1d62d7d 100644
--- a/Modules/readline.c
+++ b/Modules/readline.c
@@ -1107,7 +1107,13 @@ call_readline(FILE *sys_stdin, FILE *sys_stdout, char *prompt)
                 line = history_get(length + libedit_history_start - 1)->line;
             } else
 #endif /* __APPLE__ */
-            line = history_get(length)->line;
+            {
+                HIST_ENTRY *hist_entry = history_get(length);
+                if (hist_entry)
+                    line = hist_entry->line;
+                else
+                    line = "";
+            }
         else
             line = "";
         if (strcmp(p, line))