[vala-extra-vapis] sensors: Fix "missing return statement at end of subroutine body" errors

[Rico Tzschichholz <ricotz src gnome org>]

commit 76e4ca78288eb12024778e7ea1b6cfc8e4781927
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Sat Oct 5 10:49:48 2019 +0200

    sensors: Fix "missing return statement at end of subroutine body" errors

 sensors.vapi | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/sensors.vapi b/sensors.vapi
index 0c9cb8e..c322fe1 100644
--- a/sensors.vapi
+++ b/sensors.vapi
@@ -219,6 +219,8 @@ namespace Sensors {
             n = snprintf(bigbuf);
             if (n < 0 ) return null;
             if (n <= bigbuf.length) return (string)bigbuf;
+
+            return null;
         }
     }