virt-viewer-main: '--wait' should not be used without domain name

Commit a830275344 required the domain
name to be placed just after the '--wait' option. It broke the
command line api, because running 'virt-viewer $vm --wait' was considered
as the error.

This patch rather checks whether the domain name was specified.

Related: rhbz#1209398, rhbz#1211573

src/virt-viewer-main.c

@@ -108,6 +108,11 @@ int main(int argc, char **argv)
         goto cleanup;
     }
 
+    if (args == NULL && waitvm) {
+        g_printerr(_("\nNo DOMAIN-NAME|ID|UUID was specified for '--wait'\n\n"));
+        goto cleanup;
+    }
+
     viewer = virt_viewer_new(uri, (args) ? args[0] : NULL, direct, attach, waitvm, reconnect);
     if (viewer == NULL)
         goto cleanup;