Fix part of #5070: Display empty answer message in image click interaction

[Vishwajith-Shettigar]

Explanation

Fix part of #5070, In Image interaction UI, leave submit button enabled when answer is empty. Show an error on submitting an empty answer.

image_blank_input.webm

(Grammar error fixed )

Essential Checklist

• The PR title and explanation each start with "Fix #bugnum: " (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
• Any changes to scripts/assets files have their rationale included in the PR explanation.
• The PR follows the style guide.
• The PR does not contain any unnecessary code changes from Android Studio (reference).
• The PR is made from a branch that's not called "develop" and is up-to-date with "develop".
• The PR is assigned to the appropriate reviewers (reference).

For UI-specific PRs only

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[Vishwajith-Shettigar]

@adhiamboperes, PTAL.

[oppiabot]

Unassigning @Vishwajith-Shettigar since a re-review was requested. @Vishwajith-Shettigar, please make sure you have addressed all review comments. Thanks!

[oppiabot]

Hi @Vishwajith-Shettigar, I'm going to mark this PR as stale because it hasn't had any updates for 7 days. If no further activity occurs within 7 days, it will be automatically closed so that others can take up the issue.
If you are still working on this PR, please make a follow-up commit within 3 days (and submit it for review, if applicable). Please also let us know if you are stuck so we can help you!

[oppiabot]

Hi @Vishwajith-Shettigar, I'm going to mark this PR as stale because it hasn't had any updates for 7 days. If no further activity occurs within 7 days, it will be automatically closed so that others can take up the issue.
If you are still working on this PR, please make a follow-up commit within 3 days (and submit it for review, if applicable). Please also let us know if you are stuck so we can help you!

[oppiabot]

Hi @Vishwajith-Shettigar, I'm going to mark this PR as stale because it hasn't had any updates for 7 days. If no further activity occurs within 7 days, it will be automatically closed so that others can take up the issue.
If you are still working on this PR, please make a follow-up commit within 3 days (and submit it for review, if applicable). Please also let us know if you are stuck so we can help you!

[adhiamboperes]

Thanks @Vishwajith-Shettigar! I have left some comments.

[Vishwajith-Shettigar]

@adhiamboperes, PTAL.

[oppiabot]

Unassigning @Vishwajith-Shettigar since a re-review was requested. @Vishwajith-Shettigar, please make sure you have addressed all review comments. Thanks!

[adhiamboperes]

LGTM, thanks @Vishwajith-Shettigar!

[oppiabot]

Hi @Vishwajith-Shettigar, this PR is ready to be merged. Please address any remaining comments prior to merging, and feel free to ask someone to merge your PR once the CI checks pass and you're happy with it. Thanks!