fix: App crash while navigating back from review stats page (#766)

- Fixed a crash that occurred when pressing the back button on the Review Stats screen in low-memory scenarios.
- The issue arose because TestActivity was recreated, and while the Exam object was restored from savedInstanceState, it was not reassigned to examViewModel.
- This commit ensures the examViewModel is updated during activity recreation, preventing the crash and maintaining consistent state.

exam/src/main/java/in/testpress/exam/ui/TestActivity.java

@@ -341,6 +341,8 @@ void onDataInitialized() {
             if (exam == null) {
                 exam = courseContent.getRawExam();
                 examViewModel.setExam(exam);
+            } else {
+                examViewModel.setExam(exam);
             }
             if (courseAttempt == null && permission == null) {
                 checkPermission();