virsh-nwfilter: Update nwfilter commands to use vshCommandOptStringReq

tools/virsh-nwfilter.c

@@ -49,7 +49,7 @@ vshCommandOptNWFilterBy(vshControl *ctl, const vshCmd *cmd,
     if (!vshCmdHasOption(ctl, cmd, optname))
         return NULL;
 
-    if (vshCommandOptString(cmd, optname, &n) <= 0)
+    if (vshCommandOptStringReq(ctl, cmd, optname, &n) < 0)
         return NULL;
 
     vshDebug(ctl, VSH_ERR_INFO, "%s: found option <%s>: %s\n",
@@ -103,7 +103,7 @@ cmdNWFilterDefine(vshControl *ctl, const vshCmd *cmd)
     bool ret = true;
     char *buffer;
 
-    if (vshCommandOptString(cmd, "file", &from) <= 0)
+    if (vshCommandOptStringReq(ctl, cmd, "file", &from) < 0)
         return false;
 
     if (virFileReadAll(from, VSH_MAX_XML_FILE, &buffer) < 0)