fix exception during mouse over test

java.lang.IllegalArgumentException: Width and height must be >= 0
Width and height must be >= 0
javax.swing.plaf.basic.BasicHTML.getHTMLBaseline(Unknown Source)
javax.swing.plaf.metal.MetalToolTipUI.paint(Unknown Source)
javax.swing.plaf.ComponentUI.update(Unknown Source)
workaround for exceptions in Jung lib

java.util.ConcurrentModificationException
null
java.util.LinkedHashMap$LinkedHashIterator.nextEntry(LinkedHashMap.java:373)
java.util.LinkedHashMap$KeyIterator.next(LinkedHashMap.java:384)
java.util.Collections$UnmodifiableCollection$1.next(Collections.java:1008)
lcmc.gui.ResourceGraph$MyGraphMouseListener.graphReleased(ResourceGraph.java:1168)
edu.uci.ics.jung.visualization.control.MouseListenerTranslator.mouseReleased(MouseListenerTranslator.java:87)