Fix delete button variable name causing render crash

Author: Konvaly

debugging/book-library/script.js

@@ -89,7 +89,7 @@ function render() {
     });
 
     //add delete button to every row and render again
-    let delButton = document.createElement("button");
+    let delBut = document.createElement("button");
     delBut.id = i + 5;
     deleteCell.appendChild(delBut);
     delBut.className = "btn btn-warning";