Workaround exception in Viewer3D

While at it, some code cleanup and tweaks

src/main/java/sc/fiji/snt/gui/GuiUtils.java

@@ -740,13 +740,16 @@ public static JDialog showAboutDialog() {
 		final JLabel ijDetails = leftAlignedLabel(
 				"ImageJ " + ImageJ.VERSION + ImageJ.BUILD + "  |  Java " + System.getProperty("java.version"), "", true);
 		ijDetails.setAlignmentX(JLabel.CENTER_ALIGNMENT);
+		ijDetails.setToolTipText("Displays detailed System Information");
 		ijDetails.addMouseListener(new MouseAdapter() {
 			@Override
 			public void mouseClicked(final MouseEvent e) {
 				if (IJ.getInstance() == null)
 					new ij.plugin.JavaProperties().run("");
-				else
-					IJ.doCommand("ImageJ Properties");
+				else {
+					//IJ.doCommand("ImageJ Properties");
+					IJ.doCommand("System Information");
+				}
 			}
 
 		});

src/main/java/sc/fiji/snt/gui/cmds/PathFitterCmd.java

@@ -71,24 +71,17 @@ public class PathFitterCmd extends ContextCommand {
 	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
 	private final String msg1 = HEADER +
 		"<b>Type of refinement:</b> SNT can use the fluorescent signal around traced paths " //
-		+
-		"to optimize curvatures and estimate the thickness of traced structures. The optimization " //
-		+
-		"algorithm uses pixel intensities to fit circular cross-sections around each node. " //
-		+
-		"Once computed, fitted cross-sections can be use to: 1) Infer the radius of nodes, " //
-		+
-		"and/or 2) refine node positioning, by snapping their coordinates to the cross-section " //
-		+ "centroid.<br><br>" //
-		+
-		"Please specify the type of optimization to be performed when refining paths:";
-
+		+ "to optimize curvatures and estimate the thickness of traced structures. The optimization " //
+		+ "algorithm uses pixel intensities to fit circular cross-sections around each node. " //
+		+ "Once computed, fitted cross-sections can be use to: 1) Infer the radius of nodes, " //
+		+ "and/or 2) refine node positioning, by snapping their coordinates to the cross-section " //
+		+ "centroid. Please specify the type of optimization to be performed when refining paths:";
 	@Parameter(required = true, label = EMPTY_LABEL, choices = { CHOICE_RADII,
 		CHOICE_MIDPOINT, CHOICE_BOTH })
 	private String fitChoice;
 
-	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
-	private final String spacer = EMPTY_LABEL;
+//	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
+//	private final String spacer = EMPTY_LABEL;
 
 	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
 	private final String msg2 = HEADER +
@@ -102,17 +95,17 @@ public class PathFitterCmd extends ContextCommand {
 		+ "and repeat fitting in smaller increments")
 	private int maxRadius = PathFitter.DEFAULT_MAX_RADIUS;
 
-	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
-	private final String spacer2 = EMPTY_LABEL;
+//	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
+//	private final String spacer2 = EMPTY_LABEL;
 
 	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
 	private final String msg3 = HEADER +
 		"<b>Target image:</b> Which image should be used for fitting?";
 	@Parameter(required = false, label = EMPTY_LABEL, choices= {"Main image", "Secondary (if available)"})
 	private String impChoice;
 
-	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
-	private final String spacer3 = EMPTY_LABEL;
+//	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
+//	private final String spacer3 = EMPTY_LABEL;
 
 	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
 	private final String msg4 = HEADER +
@@ -123,13 +116,13 @@ public class PathFitterCmd extends ContextCommand {
 			"Keep original path(s)", "Replace existing nodes (undoable operation)" })
 	private String fitInPlaceChoice;
 
-	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
-	private final String spacer4 = EMPTY_LABEL;
+//	@Parameter(required = false, visibility = ItemVisibility.MESSAGE)
+//	private final String spacer4 = EMPTY_LABEL;
 
 	@Parameter(required = false, visibility = ItemVisibility.MESSAGE,
 			description="Press 'Reset' or set it to 0 to use the available processors on your computer")
 	private final String msg5 = HEADER +
-		"<b>Multithreading:</b> Number of parallel threads:";
+		"<b>Multithreading:</b> Number of parallel threads to compute fits:";
 
 	@Parameter(required = false, label = EMPTY_LABEL, persist = false, min = "0", stepSize = "1")
 	private int nThreads = SNTPrefs.getThreads();

src/main/java/sc/fiji/snt/gui/cmds/ShortcutWindowCmd.java

@@ -381,7 +381,7 @@ private boolean supported(final File file) {
 				final String filename = file.getName().toLowerCase();
 				return (filename.endsWith(".traces")) || (filename.endsWith("swc")) || (filename.endsWith(".json"));
 			}
-			
+
 			final void importFile(final File file) {
 				final Collection<Tree> trees = Tree.listFromFile(file.getAbsolutePath());
 				if (trees == null || trees.isEmpty()) {

src/main/java/sc/fiji/snt/viewer/Viewer3D.java

@@ -1781,6 +1781,8 @@ private void removeCollection(final Collection<?> collection) {
 
 	@SuppressWarnings("unchecked")
 	private List<String> getLabelsCheckedInManager() {
+		if (managerList.getCheckBoxListSelectionModel().isSelectionEmpty())
+			return Arrays.asList(new String[] {""}); // workaround Exception in getCheckBoxListSelectedValues
 		final Object[] values = managerList.getCheckBoxListSelectedValues();
 		return (List<String>) (List<?>) Arrays.asList(values);
 	}