Fixed OSC color reset without parameter->resets all colors

Adapted from (garbled) patch by wim <wim@thinkerwim.org>

Additional notes: it should reset all the colors using xloadcols().
To reproduce: set a different (theme) color using some escape code, then reset
it:

	printf '\x1b]104\x07'

st.c

@@ -1932,8 +1932,10 @@ strhandle(void)
 			if (p && !strcmp(p, "?")) {
 				osc_color_response(j, 0, 1);
 			} else if (xsetcolorname(j, p)) {
-				if (par == 104 && narg <= 1)
+				if (par == 104 && narg <= 1) {
+					xloadcols();
 					return; /* color reset without parameter */
+				}
 				fprintf(stderr, "erresc: invalid color j=%d, p=%s\n",
 				        j, p ? p : "(null)");
 			} else {