Fix duplicate, disabled "Separated Frame Below"

This commit fixes an issue where the menu option "Insert Separated
Frame Below" would show up twice, with one instance disabled. This
occurred when there was a "Standard" environment nested in a
"Frame". With this commit, the duplicate instance is removed.

(cherry picked from commit 4f7a5f8c3e)

src/frontends/qt4/Menus.cpp

@@ -1917,6 +1917,7 @@ void MenuDefinition::expandEnvironmentSeparators(BufferView const * bv,
 				translateIfPossible(prevlayout));
 		// We use command-alternatives here since this is how the binding is defined
 		// (otherwise, the binding is not displayed in the menu)
+		if (getStatus(FuncRequest(LFUN_ENVIRONMENT_SPLIT)).enabled())
 			add(MenuItem(MenuItem::Command, toqstr(label),
 				     FuncRequest(LFUN_COMMAND_ALTERNATIVES,
 						 from_ascii("environment-split ; environment-split previous"))));

status.23x

@@ -234,6 +234,8 @@ What's new
 
 - Do not allow paragraph styles in listings (bug 11127).
 
+- Fix duplicate, disabled "Separated <Environment> Below" menu item.
+
 
 * INTERNALS