Fix crash if the Help dialog was opened a second time

If it's closed with the top right close button instead of clicking the Help button again, a required flag wasn't reset, making the next click on Help try to close a nonexistent window and segfault

src/qt_gui/kbm_config_dialog.cpp

@@ -144,7 +144,7 @@ bool isHelpOpen = false;
 HelpDialog* helpDialog;
 void EditorDialog::onHelpClicked() {
     if (!isHelpOpen) {
-        helpDialog = new HelpDialog(this);
+        helpDialog = new HelpDialog(&isHelpOpen, this);
         helpDialog->setWindowTitle("Help");
         helpDialog->setAttribute(Qt::WA_DeleteOnClose); // Clean up on close
         // Get the position and size of the Config window

src/qt_gui/kbm_help_dialog.cpp

@@ -58,7 +58,13 @@ ExpandableSection::ExpandableSection(const QString& title, const QString& conten
     layout->setContentsMargins(0, 0, 0, 0);
 }
 
-HelpDialog::HelpDialog(QWidget* parent) : QDialog(parent) {
+void HelpDialog::closeEvent(QCloseEvent* event) {
+    *help_open_ptr = false;
+    close();
+}
+
+HelpDialog::HelpDialog(bool* open_flag, QWidget* parent) : QDialog(parent) {
+    help_open_ptr = open_flag;
     // Main layout for the help dialog
     QVBoxLayout* mainLayout = new QVBoxLayout(this);
 

src/qt_gui/kbm_help_dialog.h

@@ -33,9 +33,14 @@ private:
 class HelpDialog : public QDialog {
     Q_OBJECT
 public:
-    explicit HelpDialog(QWidget* parent = nullptr);
+    explicit HelpDialog(bool* open_flag = nullptr, QWidget* parent = nullptr);
+
+protected:
+    void closeEvent(QCloseEvent* event) override;
 
 private:
+    bool* help_open_ptr;
+
     QString quickstart() {
         return
             R"(The keyboard remapping backend, GUI and documentation have been written by kalaposfos