Merge metrics does not work properly

[Kolesar]

Before merging interesting part of the XML file looks like:

      <file name="/src/Exception/AliasNotFoundExceptionProcessor1.php">
        <class name="ACME\Processor\Exception\AliasNotFoundExceptionProcessor1" namespace="ACME\Processor\Exception">
          <metrics complexity="1" methods="1" coveredmethods="0" conditionals="0" coveredconditionals="0" statements="2" coveredstatements="0" elements="3" coveredelements="0"/>
        </class>
        <line num="12" type="method" name="process" visibility="public" complexity="1" crap="2.00" count="0"/>
        <line num="14" type="stmt" count="0"/>
        <line num="15" type="stmt" count="0"/>
        <metrics loc="16" ncloc="16" classes="1" methods="1" coveredmethods="0" conditionals="0" coveredconditionals="0" statements="2" coveredstatements="0" elements="3" coveredelements="0"/>
      </file>

and after merging class->metrics disappeared at all and file->metrics is changed with metrics from class->metrics, like this:

      <file name="/src/Exception/AliasNotFoundExceptionProcessor1.php">
        <class name="ACME\Processor\Exception\AliasNotFoundExceptionProcessor1" namespace="ACME\Processor\Exception"/>
        <line num="12" type="method" name="process" visibility="public" complexity="1" crap="2.00" count="0"/>
        <line num="14" type="stmt" count="0"/>
        <line num="15" type="stmt" count="0"/>
        <metrics complexity="0" elements="3" coveredelements="0" conditionals="0" coveredconditionals="0" statements="2" coveredstatements="0" methods="1" coveredmethods="0" classes="1"/>
      </file>