Bug#842213: links2: segfaults when ctrl_g pressed on a web form

[Telnet]

Package: links2
Version: 2.13-1.1

When pressing ctrl+g on a form, such as search engine input box, links2 crashes 
because of segmentation faults.
This occurs on both text mode and graphical mode.

Here is patch from links2 upstream to fix this error, reformatted as -p1 
unified diff.

--- a/url.c
+++ b/url.c
@@ -602,6 +602,7 @@ void add_conv_str(unsigned char **s, int
 unsigned char *display_url(struct terminal *term, unsigned char *url)
 {
        unsigned char *u, *uu;
+       if (!url) return stracpy(cast_uchar "");
        u = stracpy(url);
        if ((uu = cast_uchar strchr(cast_const_char u, POST_CHAR))) *uu = 0;
        return u;