Valgrind: Modernize

modernize-*

Change-Id: I6db60dce78cf2575e36caa597b1f095adba34fd9
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/valgrind/valgrindtestrunnertest.cpp

@@ -114,7 +114,7 @@ void ValgrindTestRunnerTest::cleanup()
 {
     Q_ASSERT(m_runner);
     delete m_runner;
-    m_runner = 0;
+    m_runner = nullptr;
 
     m_logMessages.clear();
     m_errors.clear();