fix possible infinite loop
Situation: incomplete multipolygon relation (some ways missing) contains 
a way which was found but also listed as 
"Sorry, no nodes found for needed way xxx"
The program fails to find a way that connects to this way 
but continues to search for ever.

git-svn-id: http://svn.mkgmap.org.uk/splitter/trunk@320 838fabe5-b1a8-4b81-9896-7a84386980e9