Don't try to put a value into a NULL pointer.
diff --git a/Python/dtoa.c b/Python/dtoa.c
index 671d027..9e3c5d8 100644
--- a/Python/dtoa.c
+++ b/Python/dtoa.c
@@ -1485,7 +1485,8 @@
        gives the total number of digits ignoring leading zeros.  A valid input
        must have at least one digit. */
     if (!nd && !lz) {
-        *se = (char *)s00;
+        if (se)
+            *se = (char *)s00;
         goto parse_error;
     }