commit 8a5ad8405024bc6cf3ae6ca0347a9e498e95016e
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..777e55f 100644
--- a/Modules/readline.c
+++ b/Modules/readline.c
@@ -1099,6 +1099,7 @@ call_readline(FILE *sys_stdin, FILE *sys_stdout, char *prompt)
     n = strlen(p);
     if (n > 0) {
         const char *line;
+        HIST_ENTRY *hist_entry;
         int length = _py_get_history_length();
         if (length > 0)
 #ifdef __APPLE__
@@ -1107,7 +1108,13 @@ 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 = history_get(length);
+                if (hist_entry)
+                    line = history_get(length)->line;
+                else
+                    line = "";
+            }