Fix return type of gettemperature

I get this error when trying to build my NixOS system with the nixos-25.05 channel:

dwmstatus.c: In function 'gettemperature':
dwmstatus.c:182:24: error: returning 'char *' from a function with return type 'int' makes integer from pointer without a cast []
  182 |                 return smprintf("");
      |                        ^~~~~~~~~~~~

dwmstatus.c

@@ -20,7 +20,6 @@
 char *tzargentina = "America/Buenos_Aires";
 char *tzutc = "UTC";
 char *tzberlin = "Europe/Berlin";
-char *tzaustin = "America/Mexico_City";
 
 static Display *dpy;
 
@@ -180,9 +179,8 @@ gettemperature(char *base, char *sensor)
 
 	co = readfile(base, sensor);
 	if (co == NULL)
-		return smprintf("");
-  return atof(co) / 1000;
-	// return smprintf("%02.0f°C", atof(co) / 1000);
+		return 0;
+	return atof(co) / 1000;
 }
 
 char *
@@ -231,7 +229,7 @@ main(void)
 		bat = getbattery("/sys/class/power_supply/BAT0");
 		// tmar = mktimes("%H:%M", tzargentina);
 		// tmutc = mktimes("%H:%M", tzutc);
-		tmbln = mktimes("%a %d %b %H:%M %Z %Y", tzaustin);
+		tmbln = mktimes("%a %d %b %H:%M %Z %Y", tzberlin);
 		// kbmap = execscript("setxkbmap -query | grep layout | cut -d':' -f 2- | tr -d ' '");
 		// surfs = execscript("surf-status");
 		t0 = gettemperature("/sys/devices/virtual/thermal/thermal_zone0", "temp");