Fix NPE

Author: mikekucera

EnrichmentMapPlugin/src/main/java/org/baderlab/csplugins/enrichmentmap/view/heatmap/HeatMapMediator.java

@@ -567,20 +567,26 @@ private GeneListTunable createGeneListTaskParams() {
 	private void runGeneMANIA() {
 		GeneListTunable geneListTaskParams = createGeneListTaskParams();
 		TaskIterator tasks = geneManiaTaskFactory.createTaskIterator(geneListTaskParams);
-		taskManager.execute(tasks);
+		if(tasks != null) {
+			taskManager.execute(tasks);
+		}
 	}
 
 	private void runString() {
 		GeneListTunable geneListTaskParams = createGeneListTaskParams();
 		TaskIterator tasks = stringAppTaskFactoy.createTaskIterator(geneListTaskParams);
-		taskManager.execute(tasks);
+		if(tasks != null) {
+			taskManager.execute(tasks);
+		}
 	}
 
 	private void runPathwayCommons() {
 		long uuid = getEnrichmentMap().getNetworkID();
 		CyNetwork network = networkManager.getNetwork(uuid);
 		OpenPathwayCommonsTask task = pathwayCommonsFactory.createForHeatMap(network);
-		taskManager.execute(new TaskIterator(task));
+		if(task != null) {
+			taskManager.execute(new TaskIterator(task));
+		}
 	}
 
 	private boolean isHeatMapPanelRegistered() {