Can't change properties for multiple objects

[alex-r-bigelow]

This is a really minor bug, but it is slowing me down a lot:

When multiple nodes or multiple edges are selected, changes in the Properties Editor only affect one of the selected items (e.g. change all the node background colors, or make all edges directed - actually there may be a separate bug there in that the arrowheads don't show up until after nodes are moved).