Parser fails when multiple classes are declared within single file

[tania-pets]

First of all, thank you for this useful action, great job!

There is an issue when the codebase contains files that declare multiple classes. The clover.xml will look something like the below:

    <file name="{filePath}">
      <class name="{class1}" namespace="global">
        <metrics complexity="3" methods="3" coveredmethods="0" conditionals="0" coveredconditionals="0" statements="6" coveredstatements="0" elements="9" coveredelements="0"/>
      </class>
      <class name="{class2}" namespace="global">
        <metrics complexity="0" methods="0" coveredmethods="0" conditionals="0" coveredconditionals="0" statements="0" coveredstatements="0" elements="0" coveredelements="0"/>
      </class>
      <line num="17" type="method" name="xxx" visibility="public" complexity="1" crap="2" count="0"/>
      .....    
      <metrics loc="43" ncloc="40" classes="1" methods="3" coveredmethods="0" conditionals="0" coveredconditionals="0" statements="6" coveredstatements="0" elements="9" coveredelements="0"/>
    </file>

That means a single <file> element will have multiple <class> children.

In that case, the parse will fail with ::error::Cannot read properties of undefined (reading '@_statements') here