another "ScToken::GetDoubleRef: virtual dummy called"

When checking for svSingleRef or svDoubleRef, also check for
svExternalSingleRef or svExternalDoubleRef. Otherwise the dummy reference is
treated.

sc/inc/token.hxx

@@ -455,7 +455,8 @@ class SingleDoubleRefModifier
 public:
                 SingleDoubleRefModifier( ScToken& rT )
                     {
-                        if ( rT.GetType() == formula::svSingleRef )
+                        formula::StackVar eType = rT.GetType();
+                        if ( eType == formula::svSingleRef || eType == formula::svExternalSingleRef )
                         {
                             pS = &rT.GetSingleRef();
                             aDub.Ref1 = aDub.Ref2 = *pS;
@@ -490,7 +491,8 @@ public:
 
                 SingleDoubleRefProvider( const ScToken& r )
                         : Ref1( r.GetSingleRef() ),
-                        Ref2( r.GetType() == formula::svDoubleRef ?
+                        Ref2( (r.GetType() == formula::svDoubleRef ||
+                                    r.GetType() == formula::svExternalDoubleRef) ?
                                 r.GetDoubleRef().Ref2 : Ref1 )
                     {}
                 SingleDoubleRefProvider( const ScSingleRefData& r )