Fix for shutdown(8) +minutes

[Nathanael Rensen]

Errant semicolon preventing shutdown(8) +minutes from working:

Index: shutdown.c
===================================================================
RCS file: /cvs/src/sbin/shutdown/shutdown.c,v
retrieving revision 1.42
diff -u -p -r1.42 shutdown.c
--- shutdown.c  18 Apr 2015 18:28:37 -0000      1.42
+++ shutdown.c  23 Apr 2015 01:59:48 -0000
@@ -440,7 +440,7 @@ getoffset(char *timearg)
                const char *errstr;
 
                offset = strtonum(++timearg, 0, INT_MAX, &errstr);
-               if (errstr);
+               if (errstr)
                        badtime();
                offset *= 60;
                shuttime = now + offset;