Fix NPE when includeStdTypes flag is set, and clean goal is not specified

[spensonshih]

Description

Fixing a NullPointerException when running the goal repeatedly without clean.

Changes Made

The NullPointerException is due to an uninitialized variable for the protocVersion when the plugin detected proto files remain unchanged since last compilation, but the includeStdTypes flag is set.

This pull requests adds the includeStdTypes flag check to prevent the NPE.

Definition of Done

Before submitting this pull request, please ensure that the following criteria have been met:

• All automated tests have passed successfully.
• All manual tests have passed successfully.
• Code has been reviewed by at least one other team member.
• Code has been properly documented and commented as needed.
• All new and existing code adheres to our project's coding standards.
• All dependencies have been added or removed from the project's README or other documentation as needed.
• Any relevant documentation or help files have been updated to reflect the changes made in this pull request.
• Any necessary database migrations have been run.
• Any relevant UI changes have been reviewed and approved by the UI/UX team.

[ee08b397]

The change looks good. I found a similar change about "Use of breaks " from the original repo at
os72/protoc-jar-maven-plugin#40.

Found the same change to <includeStdTypes>true</includeStdTypes> in this blog
https://blog.jetbrains.com/idea/2023/05/how-to-work-with-protobuf-maven-projects-in-intellij-idea/

[wchen-55e]

LGTM