ICU-21667 Fix coverity warnings

[mike-fabian]

See: https://unicode-org.atlassian.net/browse/ICU-21667 (Issues found by coverity in icu-69.1)

Checklist

• [x] Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-21667
• [x] Required: The PR title must be prefixed with a JIRA Issue number.
• [x] Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
• [x] Required: Each commit message must be prefixed with a JIRA Issue number.
• [ ] Issue accepted (done by Technical Committee after discussion)
• [ ] Tests included, if applicable
• [ ] API docs and/or User Guide docs changed or added, if applicable

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[FrankYFTang]

sorry, I was just busy on review the other PR recently. Will take a closer look about this soon.

[FrankYFTang]

really appreciate you work on this. There are a lot of old code which use raw pointers we should migrate to use smart pointer instead.

[FrankYFTang]

@mike-fabian thank you for working on this. I will take a 15 days vacation Sep 19-Oct 4 and won't be able to review during that period of time. The freeze for ICU70.1 is coming soon. If you can revise this PR this week I may be able to review again and land it after you address all the issues. Thanks

[FrankYFTang]

@mike-fabian do you still want to work on this? I am waiting for your revision to review :) Thanks for all your hard work

[FrankYFTang]

ping