ofz#6180 Integer-overflow

Change-Id: I6339a6ebb188dc9e7bccfa629a40af8e67c13feb
Reviewed-on: https://gerrit.libreoffice.org/49487Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

include/xmloff/unointerfacetouniqueidentifiermapper.hxx

@@ -75,7 +75,7 @@ private:
     void insertReference( const OUString& rIdentifier, const css::uno::Reference< css::uno::XInterface >& rInterface );
 
     IdMap_t maEntries;
-    sal_Int32 mnNextId;
+    sal_uInt32 mnNextId;
 };
 
 }

xmloff/source/core/unointerfacetouniqueidentifiermapper.cxx

@@ -166,7 +166,7 @@ void UnoInterfaceToUniqueIdentifierMapper::insertReference( const OUString& rIde
     // so we make sure we will never generate
     // an integer value like this one
     sal_Int32 nId = rIdentifier.copy(2).toInt32();
-    if( mnNextId <= nId )
+    if (nId > 0 && mnNextId <= static_cast<sal_uInt32>(nId))
         mnNextId = nId + 1;
 }