wxGUI/lmgr: hide map layer menu item 'Change opacity level' if 3d vie…

…w is activated. (OSGeo#2697)

* wxGUI/lmgr: hide map layer menu item 'Change opacity level'

If 3d view is activated.

gui/wxpython/lmgr/layertree.py

@@ -491,7 +491,7 @@ def OnLayerContextMenu(self, event):
         if ltype not in ("group", "command"):
             if numSelected == 1:
                 self.popupMenu.AppendSeparator()
-                if ltype != "raster_3d":
+                if not (ltype == "raster_3d" or self.mapdisplay.IsPaneShown("3d")):
                     item = wx.MenuItem(
                         self.popupMenu,
                         id=self.popupID["opacity"],