First time opening visu does not work

[CyrilFerlicot]

Tested with TelescopeCytoscape.

Executing this:

visu := TLVisualization new.
visu addNodesFromEntities: (1 to: 20).
visu open

does not open any visu the first time.

Then executing this:

visu := TLVisualization new.
visu addNodesFromEntities: (1 to: 20).
visu styleSheet
	width: 40;
	height: 40;
	nodeLabel: #asString.
visu open

will work and after that the first one also work.