fix(exam): fix startexam function (not finding examdata)

context/ExamContext.tsx

@@ -86,18 +86,21 @@ export const ExamProvider: React.FC<{ children: ReactNode }> = ({
     setCurrentAttemptState(null);
   };
 
-  const startExam = () => {
-    if (!currentExam) {
+  const startExam = (exam?: Exam) => {
+    const examToUse = exam || currentExam;
+
+    if (!examToUse) {
       console.warn("No exam selected, redirecting to /unit");
       router.push("/unit");
       return;
     }
 
     const attempt: ExamAttempt = {
-      examId: currentExam.id,
-      exam: currentExam,
+      examId: examToUse.id,
+      exam: examToUse,
       answers: [],
       startTime: new Date(),
+      totalQuestions: 0,
     };
 
     setCurrentAttemptState(attempt);