PR 21417, ar arg check failure

PR 21417
	* ar.c (main): Check that an archive file is given after options.

binutils/ChangeLog

@@ -1,3 +1,8 @@
+2017-04-23  Alan Modra  <amodra@gmail.com>
+
+	PR 21417
+	* ar.c (main): Check that an archive file is given after options.
+
 2017-04-23  Alan Modra  <amodra@gmail.com>
 
 	PR 21415

binutils/ar.c

@@ -788,6 +788,8 @@ main (int argc, char **argv)
 	}
 
       inarch_filename = argv[arg_index++];
+      if (inarch_filename == NULL)
+	usage (0);
 
       for (file_count = 0; argv[arg_index + file_count] != NULL; file_count++)
 	continue;