Fix two minor UI problems in the Bombs demo

Error 1: When enabling/disabling easy corner, the enable/disable text
was mixed up. This resulted in being asked to confirm disabling easy
corner, when it was being enabled, and vice versa.

Error 2: When choosing not to switch easy corner, the checkmark in the
menu showing it's state still swapped.

Fix 1: Swap the text for enable/disable in the confirm easy mode toggle
dialog box.

Fix 2: Call GetMenuBar()->Check(bombsID_EASYCORNER, m_easyCorner);
(Check always returns void, and GetMenuBar is only called from the
MenuBar, after it's been set up) to set the checkmark's state, when
needed.

Closes #22764.

demos/bombs/bombs.cpp

@@ -183,9 +183,9 @@ void BombsFrame::OnEasyCorner(wxCommandEvent& WXUNUSED(event))
 {
     wxString msg;
     if(m_easyCorner)
-        msg = wxT("enable");
-    else
         msg = wxT("disable");
+    else
+        msg = wxT("enable");
 
     msg = wxT("Do you really want to ") + msg + wxT(" having\ntop left corner always empty for easier start?");
 
@@ -196,7 +196,12 @@ void BombsFrame::OnEasyCorner(wxCommandEvent& WXUNUSED(event))
                this
              );
 
-    if(ok!=wxYES)return;
+    if(ok!=wxYES)
+    {
+        // Undo the automatic change to the menu bar, keeping it in sync with the actual option value.
+        GetMenuBar()->Check(bombsID_EASYCORNER, m_easyCorner);
+        return;
+    }
 
     m_easyCorner = !m_easyCorner;