added modal to handle error in exponent calculator

[maura-dev]

Related Issue

• This is an update to PR#611 to ensure proper error handling

Fixes: #564

Describe the changes you've made

I added a modal to inform user when one of the inputs required is missing

Checklist:

• [x ] My code follows the style guidelines of this project.
• [ x] I have performed a self-review of my own code.
• [x ] I have commented my code, particularly in hard-to-understand areas.
• [x ] My changes generate no new warnings.

Screenshots

[github-actions[bot]]

Our team will soon review your PR. Thanks @maura-dev :)

[github-actions[bot]]

Thank you @maura-dev for taking out your valuable time in order to contribute to our project. Looking forward for more such amazing contributions :).