[hackers] [st] Fix null pointer access in strhandle || Jochen Sprickerhof

[git]

commit a0467c802d4f86ed162486e3453dd61181423902
Author:     Jochen Sprickerhof <g...@jochen.sprickerhof.de>
AuthorDate: Mon Dec 27 11:41:42 2021 +0100
Commit:     Hiltjo Posthuma <hil...@codemadness.org>
CommitDate: Mon Dec 27 13:07:11 2021 +0100

    Fix null pointer access in strhandle
    
    According to the spec the argument is optional for 104, so p can be
    NULL as can be tested with printf '\x1b]104\x07'. This is a regression
    of 8e31030.

diff --git a/st.c b/st.c
index 6783c2b..de2dd0e 100644
--- a/st.c
+++ b/st.c
@@ -1960,10 +1960,10 @@ strhandle(void)
                                break;
                        p = strescseq.args[2];
                        /* FALLTHROUGH */
-               case 104: /* color reset, here p = NULL */
+               case 104: /* color reset */
                        j = (narg > 1) ? atoi(strescseq.args[1]) : -1;
 
-                       if (!strcmp(p, "?"))
+                       if (p && !strcmp(p, "?"))
                                osc4_color_response(j);
                        else if (xsetcolorname(j, p)) {
                                if (par == 104 && narg <= 1)