fix possible npe in CRM Graph

java.lang.NullPointerException

null
lcmc.gui.CRMGraph.getHbConnections(CRMGraph.java:292)
lcmc.gui.resources.GroupInfo.getSubtextsForGraph(GroupInfo.java:891)
lcmc.gui.CRMGraph.getSubtexts(CRMGraph.java:1806)
lcmc.gui.ResourceGraph$MyPluggableRenderer.paintShapeForVertex(ResourceGraph.java:1421)