Fix signal connection nodiscard warnings (#4818)

src/widgets/splits/SplitInput.hpp

@@ -91,6 +91,9 @@ protected:
     void addShortcuts() override;
     void initLayout();
     bool eventFilter(QObject *obj, QEvent *event) override;
+#ifdef DEBUG
+    bool keyPressedEventInstalled{};
+#endif
     void installKeyPressedEvent();
     void onCursorPositionChanged();
     void onTextChanged();