Remove redundant null checks

Attempting to delete a null pointer is a noop in C++.

Closes #2864.

[1] https://isocpp.org/wiki/faq/freestore-mgmt#delete-handles-null

src/gui/mainwindow.cpp

@@ -678,7 +678,7 @@ void MainWindow::displayRSSTab(bool enable)
 #endif
         }
     }
-    else if (m_rssWidget) {
+    else {
         delete m_rssWidget;
     }
 }
@@ -714,7 +714,7 @@ void MainWindow::displaySearchTab(bool enable)
                 tr("Search"));
         }
     }
-    else if (m_searchWidget) {
+    else {
         delete m_searchWidget;
     }
 }
@@ -1170,8 +1170,7 @@ void MainWindow::closeEvent(QCloseEvent *e)
     }
 
     // abort search if any
-    if (m_searchWidget)
-        delete m_searchWidget;
+    delete m_searchWidget;
 
     hide();
 #ifndef Q_OS_MACOS
@@ -1875,7 +1874,7 @@ void MainWindow::on_actionExecutionLogs_triggered(bool checked)
         m_tabs->setTabIcon(indexTab, UIThemeManager::instance()->getIcon("view-calendar-journal"));
 #endif
     }
-    else if (m_executionLog) {
+    else {
         delete m_executionLog;
     }
 

src/gui/private/fspathedit_p.cpp

@@ -259,10 +259,8 @@ void Private::FileLineEdit::keyPressEvent(QKeyEvent *e)
         FileSystemPathValidator::TestResult lastTestResult = validator->lastTestResult();
         QValidator::State lastState = validator->lastValidationState();
         if (lastTestResult == FileSystemPathValidator::TestResult::OK) {
-            if (m_warningAction) {
-                delete m_warningAction;
-                m_warningAction = nullptr;
-            }
+            delete m_warningAction;
+            m_warningAction = nullptr;
         }
         else {
             if (!m_warningAction) {

src/gui/uithememanager.cpp

@@ -43,10 +43,8 @@ UIThemeManager *UIThemeManager::m_instance = nullptr;
 
 void UIThemeManager::freeInstance()
 {
-    if (m_instance) {
-        delete m_instance;
-        m_instance = nullptr;
-    }
+    delete m_instance;
+    m_instance = nullptr;
 }
 
 void UIThemeManager::initInstance()