Fix rubocop issues

Author: adangel

lib/pmdtester/parsers/pmd_report_document.rb

@@ -56,7 +56,7 @@ def end_element(name)
         @violations.add_violations_by_filename(@current_filename, @current_violations)
         @current_filename = nil
       when 'violation'
-        @current_violation&.text.strip!
+        @current_violation.text.strip!
         @current_violations.push(@current_violation) if match_filter_set?(@current_violation)
         @current_violation = nil
       when 'error'

test/test_pmd_report_document.rb

@@ -4,12 +4,15 @@
 
 class TestPmdReportDocument < Test::Unit::TestCase
   include PmdTester
+
+  FIRST_FILE = '/target/repositories/spring-framework/gradle/jdiff/Null.java'
+
   def test_document
     doc = PmdReportDocument.new('base', 'SHOULD_BE_REPLACED')
     parser = Nokogiri::XML::SAX::Parser.new(doc)
     parser.parse(File.open('test/resources/pmd_report_document/test_document.xml'))
     assert_equal(8, doc.violations.violations_size)
-    assert_equal('Document \'empty\' constructor', doc.violations.violations['/target/repositories/spring-framework/gradle/jdiff/Null.java'][0].text)
+    assert_equal('Document \'empty\' constructor', doc.violations.violations[FIRST_FILE][0].text)
     assert_equal(2, doc.errors.errors_size)
     pmd_errors = doc.errors.errors.values
     assert_not_nil(pmd_errors[0])