FIXUP: <#54 (review)>

src/tz_macos.rs

@@ -11,9 +11,12 @@ unsafe fn get_timezone() -> Option<String> {
     // The longest name in the IANA time zone database is 25 ASCII characters long.
     const MAX_LEN: usize = 32;
 
-    // Get system time zone, and its name.
+    // Get system time zone, and borrow its name.
     let tz = Dropping::new(CFTimeZoneCopySystem())?;
-    let name = Dropping::new(CFTimeZoneGetName(tz.0))?;
+    let name = match CFTimeZoneGetName(tz.0) {
+        name if !name.is_null() => name,
+        _ => return None,
+    };
 
     // Copy the name into the buffer.
     let mut buf = [0; MAX_LEN];