clustering selected nodes doesn't work properly #8

Steps to reproduce:

• Open a network (eg galFiltered)
• Select a subset of the nodes
• Run mcl with selectedNodes=true
• Result only the selected nodes are clustered, so far so good
• Unselect the nodes
• Run mcl with selectedNodes = false
• Result is that only the nodes that were previously selected are clustered

The behaviour seems to be that whenever you run mcl on some selected nodes, any subsequent call to mcl always runs on the same nodes as the first time.