URGENT: Quick bug fix for the duplicate indicator

(cherry picked from commit 2ec3ba46628687e9165df1df30d9384b14a50770)
diff --git a/index.html b/index.html
index 779fb60..48c3b25 100644
--- a/index.html
+++ b/index.html
@@ -164,7 +164,7 @@
 
                         if (i > 0 && data.payload.classes[i-1].friendly_name == classe.friendly_name) {
                             div1.classList.add('has-text-danger', 'has-text-weight-bold');
-                        } else if (data.payload.classes.length >= i && data.payload.classes[i+1].friendly_name == classe.friendly_name) {
+                        } else if (i < data.payload.classes.length - 1 && data.payload.classes[i+1].friendly_name == classe.friendly_name) {
                             div1.classList.add('has-text-danger', 'has-text-weight-bold');
                         }