Linux: Fix crash if user is able to close the waiting dialog before the operation is finished. This can happen if GTK installation show "X" closing icon even if it is programmatically disabled (e.g. on Lubuntu 16.04)

src/Main/Forms/WaitDialog.h

@@ -1,5 +1,5 @@
 /*
- Copyright (c) 2013-2017 IDRIX. All rights reserved.
+ Copyright (c) 2013-2018 IDRIX. All rights reserved.
 
  Governed by the Apache License 2.0 the full text of which is
  contained in the file License.txt included in VeraCrypt binary and source
@@ -47,7 +47,7 @@ namespace VeraCrypt
 	{
 	public:
 		WaitDialog (wxWindow *parent, const wxString& label, WaitThreadRoutine* pRoutine)
-			: WaitDialogBase(parent), WaitThreadUI(pRoutine), m_timer (this)
+			: WaitDialogBase(parent), WaitThreadUI(pRoutine), m_bThreadRunning (false), m_timer (this)
 		{
 			WaitStaticText->SetLabel (label);
 			WaitProgessBar->Pulse();
@@ -76,6 +76,7 @@ namespace VeraCrypt
 		{
 			m_thread->Run();
 			m_timer.Start(100);
+			m_bThreadRunning = true;
 		}
 
 		int GetCharWidth (wxWindow *window) const
@@ -144,9 +145,19 @@ namespace VeraCrypt
 				pin = wxT("");
 		}
 
-		// virtual void OnWaitDialogClose( wxCloseEvent& event ) { }
+		virtual void OnWaitDialogClose( wxCloseEvent& event ) 
+		{ 
+			if (event.CanVeto () && m_bThreadRunning)
+			{
+				event.Veto ();
+			}
+			else
+				event.Skip ();
+		}
+ 
 		void OnThreadCompletion(wxCommandEvent &)
 		{
+			m_bThreadRunning = false;
 			m_queue.Clear();
 			EndModal(0);
 		}
@@ -202,6 +213,7 @@ namespace VeraCrypt
 
 	protected:
 		WaitThread* m_thread;
+		bool m_bThreadRunning;
 		wxTimer m_timer;
 		wxMessageQueue<wxString> m_queue;
 	};