AutoTest: Fix some clazy warnings

Avoids potential nullptr accesses and unneeded allocations.

Change-Id: I8c13ca1dab885fc3e9a05dc7329ff592a7f0fe1a
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/autotest/autotestunittests.cpp

@@ -80,7 +80,7 @@ void AutoTestUnitTests::initTestCase()
 
     m_tmpDir = new CppTools::Tests::TemporaryCopiedDir(":/unit_test");
 
-    if (!qgetenv("BOOST_INCLUDE_DIR").isEmpty()) {
+    if (!qEnvironmentVariableIsEmpty("BOOST_INCLUDE_DIR")) {
         m_checkBoost = true;
     } else {
         if (Utils::HostOsInfo::isLinuxHost()
@@ -200,7 +200,7 @@ void AutoTestUnitTests::testCodeParserSwitchStartup_data()
 
 void AutoTestUnitTests::testCodeParserGTest()
 {
-    if (qgetenv("GOOGLETEST_DIR").isEmpty())
+    if (qEnvironmentVariableIsEmpty("GOOGLETEST_DIR"))
         QSKIP("This test needs googletest - set GOOGLETEST_DIR (point to googletest repository)");
 
     QFETCH(QString, projectFilePath);

src/plugins/autotest/catch/catchconfiguration.cpp

@@ -74,6 +74,7 @@ static QStringList filterInterfering(const QStringList &provided, QStringList *o
     for (const auto &arg : provided) {
         bool interferes = false;
         if (filterNext) {
+            if (omitted)
                 omitted->append(arg);
             filterNext = false;
             continue;

src/plugins/autotest/testtreemodel.cpp

@@ -254,6 +254,7 @@ void TestTreeModel::onBuildSystemTestsUpdated()
     if (!bs || !bs->project())
         return;
 
+    QTC_ASSERT(m_checkStateCache, return);
     m_checkStateCache->evolve(ITestBase::Tool);
 
     ITestTool *testTool = TestFrameworkManager::testToolForBuildSystemId(bs->project()->id());