fix(diktat-maven-plugin): Maven projects with non local parent POM

[agebhar1]

In 1 support for mulimodule Maven projects are introduced. But fails for Maven projects with non local parent POM like Spring Boot projects:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  …
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.2.4</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>
  …
</project>

Invoke mvn diktat:{check|fix} fails with:

[ERROR] Failed to execute goal com.saveourtool.diktat:diktat-maven-plugin:2.0.0:fix (default-cli) on project …: Execution default-cli of goal com.saveourtool.diktat:diktat-maven-plugin:2.0.0:fix failed: Cannot invoke "java.io.File.toPath()" because the return value of "org.apache.maven.project.MavenProject.getBasedir()" is null -> [Help 1]

Fixes #1893.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 76.62%. Comparing base (8d61ddf) to head (9ebfbac).

Files	Patch %	Lines
.../saveourtool/diktat/plugin/maven/DiktatBaseMojo.kt	0.00%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1924      +/-   ##
============================================
- Coverage     76.67%   76.62%   -0.05%     
  Complexity     2492     2492              
============================================
  Files           134      134              
  Lines          7914     7919       +5     
  Branches       2240     2240              
============================================
  Hits           6068     6068              
- Misses          841      846       +5     
  Partials       1005     1005              

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[orchestr7]

Awesome, thank you! @nulls pls review also

[orchestr7]

I also think we need to make the release with this change

[agebhar1]

Awesome, thank you! @nulls pls review also

With pleasure!