commit 56a60ee50122613d3a356ce74b4bd77b5e7be235
Author: Tim Kosse <tim.kosse@filezilla-project.org>
Date:   Sat Aug 26 15:37:30 2017 +0200

    If a wxTopLevelWindow has been instanced, but Create has not been called, calling Destroy on the window results in an assertion in Show(false), at least under wxGTK. Fix this by only hiding a top level window during destruction if it is actually shown.

diff --git a/src/common/toplvcmn.cpp b/src/common/toplvcmn.cpp
index ef693690c5..8d07812031 100644
--- a/src/common/toplvcmn.cpp
+++ b/src/common/toplvcmn.cpp
@@ -122,19 +122,21 @@ bool wxTopLevelWindowBase::Destroy()
     // any more as no events will be sent to the hidden window and without idle
     // events we won't prune wxPendingDelete list and the application won't
     // terminate
-    for ( wxWindowList::const_iterator i = wxTopLevelWindows.begin(),
-                                     end = wxTopLevelWindows.end();
-          i != end;
-          ++i )
-    {
-        wxTopLevelWindow * const win = static_cast<wxTopLevelWindow *>(*i);
-        if ( win != this && win->IsShown() )
+    if ( IsShown() ) {
+        for ( wxWindowList::const_iterator i = wxTopLevelWindows.begin(),
+                                         end = wxTopLevelWindows.end();
+              i != end;
+              ++i )
         {
-            // there remains at least one other visible TLW, we can hide this
-            // one
-            Hide();
+            wxTopLevelWindow * const win = static_cast<wxTopLevelWindow *>(*i);
+            if ( win != this && win->IsShown() )
+            {
+                // there remains at least one other visible TLW, we can hide this
+                // one
+                Hide();
 
-            break;
+                break;
+            }
         }
     }