Prevent /usr/bin/grops from dumping core with given an invalid argument value
with something such as

 $ /usr/bin/grops -c a

Fix has been submitted upstream:
http://savannah.gnu.org/bugs/?42190

--- groff-1.22.2/src/devices/grops/ps.cpp.orig	2014-04-24 06:01:32.421674773 -0700
+++ groff-1.22.2/src/devices/grops/ps.cpp	2014-04-24 09:27:56.445423217 -0700
@@ -1803,7 +1803,7 @@
       break;
     case 'c':
       if (sscanf(optarg, "%d", &ncopies) != 1 || ncopies <= 0) {
-	error("bad number of copies `%s'", optarg);
+	error("bad number of copies `%1'", optarg);
 	ncopies = 1;
       }
       break;