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.

1 files changed, 2 insertions, 2 deletions

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)