diff --git a/frontend/app.js b/frontend/app.js
index 1e08938..913ef2e 100644
--- a/frontend/app.js
+++ b/frontend/app.js
@@ -1877,6 +1877,7 @@ class TooltipManager {
   }
 
   handleMouseEnter(e) {
+    if (!e.target || !e.target.closest) return;
     const trigger = e.target.closest(".info-trigger");
     if (!trigger) return;
 
@@ -1887,6 +1888,7 @@ class TooltipManager {
   }
 
   handleMouseLeave(e) {
+    if (!e.target || !e.target.closest) return;
     const trigger = e.target.closest(".info-trigger");
     const tooltip = e.target.closest(".tooltip");
 
@@ -1895,8 +1897,8 @@ class TooltipManager {
     // Check if moving between trigger and tooltip
     const relatedTarget = e.relatedTarget;
     if (
-      relatedTarget?.closest(".info-trigger") === this.activeTooltip ||
-      relatedTarget?.closest(".tooltip")
+      relatedTarget?.closest?.(".info-trigger") === this.activeTooltip ||
+      relatedTarget?.closest?.(".tooltip")
     ) {
       return;
     }
@@ -1908,6 +1910,7 @@ class TooltipManager {
   }
 
   handleFocusIn(e) {
+    if (!e.target || !e.target.closest) return;
     const trigger = e.target.closest(".info-trigger");
     if (!trigger) return;
 
@@ -1916,6 +1919,7 @@ class TooltipManager {
   }
 
   handleFocusOut(e) {
+    if (!e.target || !e.target.closest) return;
     const trigger = e.target.closest(".info-trigger");
     if (!trigger) return;