fix: quiz evalutation issue (#25671)

diff --git a/erpnext/public/js/education/lms/quiz.js b/erpnext/public/js/education/lms/quiz.js
index 32fa4ab..5683f73 100644
--- a/erpnext/public/js/education/lms/quiz.js
+++ b/erpnext/public/js/education/lms/quiz.js
@@ -118,7 +118,7 @@
 			quiz_response: this.get_selected(),
 			course: this.course,
 			program: this.program,
-			time_taken: this.is_time_bound ? this.time_taken : ""
+			time_taken: this.is_time_bound ? this.time_taken : 0
 		}).then(res => {
 			this.submit_btn.remove()
 			if (!res.message) {