tdf#77241: sw: fix creation of field data source string

SwChangeDBDlg::UpdateFlds() depends on undefined behaviour in
constructing sTemp, because the call to GetDBName initializes local
variables that are already used in other sub-expressions of the
statement.

(regression from 8a7a9992)

Change-Id: Ibf8c0091da672e133d7a35bc61c059eaf65a3bc2
Reviewed-on: https://gerrit.libreoffice.org/14302Reviewed-by: Lionel Elie Mamane <lionel@mamane.lu>
Tested-by: Lionel Elie Mamane <lionel@mamane.lu>

sw/source/ui/fldui/changedb.cxx

@@ -192,7 +192,8 @@ void SwChangeDBDlg::UpdateFlds()
     OUString sTableName;
     OUString sColumnName;
     sal_Bool bIsTable = sal_False;
-    const OUString sTemp = m_pAvailDBTLB->GetDBName(sTableName, sColumnName, &bIsTable)
+    const OUString DBName(m_pAvailDBTLB->GetDBName(sTableName, sColumnName, &bIsTable));
+    const OUString sTemp = DBName
         + OUString(DB_DELIM)
         + sTableName
         + OUString(DB_DELIM)