Call PTRACE_CONT with addr=0

* strace.c (trace): Call PTRACE_CONT with addr=0.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/strace.c b/strace.c
index e627a5e..727e490 100644
--- a/strace.c
+++ b/strace.c
@@ -1809,7 +1809,7 @@
 				   CLONE_PTRACE itself.  */
 			{
 				if (WIFSTOPPED(status))
-					ptrace(PTRACE_CONT, pid, (char *) 1, 0);
+					ptrace(PTRACE_CONT, pid, (char *) 0, 0);
 				error_msg_and_die("Unknown pid: %u", pid);
 			}
 		}