--- a/s4-main.js	Sat May 28 22:58:06 2022 +0900
+++ b/s4-main.js	Sat May 28 23:18:43 2022 +0900
@@ -1035,13 +1035,16 @@
     }
     function initReplyHover() {
 	function getTextById(id) {
-	    let repltd = document.getElementById(id),
-		txt = repltd.innerText,
-		authtd = repltd.parentNode.getElementsByTagName("td")[0],
-		authAs = authtd.getElementsByTagName("a"),
-		author = authAs[authAs.length-1].innerText,
-		digest = txt.split("\n").splice(0, hoverTextLines).join("\n");
-	    return "[[ "+author+" ]]\n"+digest;
+	    let repltd = document.getElementById(id);
+	    if (repltd) {
+		let txt = repltd.innerText,
+		    authtd = repltd.parentNode.getElementsByTagName("td")[0],
+		    authAs = authtd.getElementsByTagName("a"),
+		    author = authAs[authAs.length-1].innerText,
+		    digest = txt.split("\n").splice(0, hoverTextLines).join("\n");
+		return "[[ "+author+" ]]\n"+digest;
+	    } else
+		return "";
 	}
 	for (let td of document.querySelectorAll("td.repl")) {
 	    let text = td.innerHTML;