Resolves: tdf#101691 re-intern strings of external formula results

If the external cell referenced is a formula result of type string that
string needs to be re-interned for the reference cache as well.

Change-Id: Iea3c3d777dede2ad6ba0b084533af964da991ca6

sc/source/ui/docshell/externalrefmgr.cxx

@@ -1557,8 +1557,8 @@ static FormulaToken* convertToToken( ScDocument* pHostDoc, ScDocument* pSrcDoc,
             }
             else
             {
-                svl::SharedString aStr = pFCell->GetString();
-                return new formula::FormulaStringToken(aStr);
+                svl::SharedString aSS = pHostDoc->GetSharedStringPool().intern( pFCell->GetString().getString());
+                return new formula::FormulaStringToken(aSS);
             }
         }
         default: