Fix Assistant crash when closing last tab.

Disable 'Close Tab' action from 'File' menu for last tab to avoid
crash. Context menu 'close' actions in "open pages" widget, are already
disabled under same conditions.

Manually cherry-picked from Qt5:
Change I7f285f45: Fix Assistant crash when closing last tab

Task-number: QTBUG-23986

Change-Id: I0176451c80f0d25e82c7cd4fb2076c23c9d50128
Reviewed-by: Janne Anttila <janne.anttila@digia.com>
Reviewed-by: Karsten Heimrich <karsten.heimrich@nokia.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>

2 files changed, 11 insertions, 0 deletions

diff --git a/tools/assistant/tools/assistant/mainwindow.cpp b/tools/assistant/tools/assistant/mainwindow.cpp
index d054855..c10a481 100644
--- a/tools/assistant/tools/assistant/mainwindow.cpp
+++ b/tools/assistant/tools/assistant/mainwindow.cpp
@@ -440,6 +440,7 @@ void MainWindow::setupActions()
 #endif
 
     QMenu *menu = menuBar()->addMenu(tr("&File"));
+    connect(menu, SIGNAL(aboutToShow()), this, SLOT(aboutToShowFileMenu()));
 
     OpenPagesManager * const openPages = OpenPagesManager::instance();
     m_newTabAction
@@ -1096,4 +1097,13 @@ void MainWindow::registerDocumentation(const QString &component,
     }
 }
 
+void MainWindow::aboutToShowFileMenu()
+{
+    OpenPagesManager * const openPages = OpenPagesManager::instance();
+    if (openPages->pageCount() > 1)
+        m_closeTabAction->setEnabled(true);
+    else
+        m_closeTabAction->setEnabled(false);
+}
+
 QT_END_NAMESPACE
diff --git a/tools/assistant/tools/assistant/mainwindow.h b/tools/assistant/tools/assistant/mainwindow.h
index 68b9c2a..bb40d92 100644
--- a/tools/assistant/tools/assistant/mainwindow.h
+++ b/tools/assistant/tools/assistant/mainwindow.h
@@ -136,6 +136,7 @@ private:
 private slots:
     void showBookmarksDockWidget();
     void hideBookmarksDockWidget();
+    void aboutToShowFileMenu();
 
 private:
     QWidget *m_bookmarkWidget;