Fixed the error of upper top closing of exit message

[akash-rajak]

Issue Number

fixes #100

Describe the changes you've made

Earlier the code was using one boolean variable ans, when it becomes true, then only closes, i removed that ans variable checking and applied messagebox.askokcancel, instead of messagebox.askyesno

Describe if there is any unusual behaviour of your code(Write NA if there isn't)

NA

Additional context (OPTIONAL)

Add any other context or screenshots about the feature request here.

Test plan (OPTIONAL)

A good test plan should give instructions that someone else can easily follow. How someone can test your code?

Checklist

• [ ] I have added my name in the contributors list at the end of README.md file.
• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.
• [x] The title of my pull request is a short description of the requested changes.
• [ ] Open Source Program names(OPTIONAL: If you participated in any open-source program then please mention the program name here)

Below is the screen shot of bug correction, screenshot with bug,

screenshot after correction,

[akash-rajak]

@QAZIMAAZARSHAD , i have fixed error of not showing close option at top right of exit message box, check it.