undo: Clear undo stack on file close

The undo stack is only relevant to the dives that were loaded at the
time the command was executed. If a file is closed, by specifically
closing it or opening another file, then the undo commands will
reference dives that aren't available anymore. Clearing the undo stack
ensures that we don't crash or accidentally do some undefined
modifications to the currently open file.

Signed-off-by: Michael Andreen <michael@andreen.dev>

CHANGELOG.md

@@ -1,4 +1,5 @@
 - Desktop: Allow more than one media file to be imported from web
+- undo: Clear undo stack when the current file is closed
 ---
 * Always add new entries at the very top of this file above other existing entries and this note.
 * Use this layout for new entries: `[Area]: [Details about the change] [reference thread / issue]`

commands/command_base.cpp

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#include "command.h"
 #include "command_base.h"
 #include "core/globals.h"
 #include "core/qthelper.h" // for updateWindowTitle()
@@ -18,6 +19,7 @@ void init()
 {
 	undoStack = make_global<QUndoStack>();
 	QObject::connect(undoStack, &QUndoStack::cleanChanged, &updateWindowTitle);
+	QObject::connect(&diveListNotifier, &DiveListNotifier::dataReset, &Command::clear);
 	changesCallback = &changesMade;
 }
 

desktop-widgets/mainwindow.cpp

@@ -513,7 +513,6 @@ void MainWindow::closeCurrentFile()
 	if (!existing_filename)
 		setTitle();
 	disableShortcuts();
-	Command::setClean();
 }
 
 void MainWindow::updateCloudOnlineStatus()