Properly disable plugin, throw custom exception when plugin is incompatible

src/com/cnaude/chairs/core/Chairs.java

@@ -64,7 +64,6 @@ public class Chairs extends JavaPlugin {
 			nmsaccess.setupVehicleArrow();
 		} catch (Exception e) {
 			e.printStackTrace();
-			log.severe("Failed to generate VehicleArrow class, exiting");
 			getServer().getPluginManager().disablePlugin(this);
 			return;
 		}
@@ -91,6 +90,7 @@ public class Chairs extends JavaPlugin {
 
 	@Override
 	public void onDisable() {
+		if (psitdata != null) {
 			for (Player player : getServer().getOnlinePlayers()) {
 				if (psitdata.isSitting(player)) {
 					PlayerChairUnsitEvent playerunsitevent = new PlayerChairUnsitEvent(player, false);
@@ -98,6 +98,7 @@ public class Chairs extends JavaPlugin {
 					psitdata.unsitPlayerNow(player);
 				}
 			}
+		}
 		if (ignoreList != null) {
 			ignoreList.save();
 		}

src/com/cnaude/chairs/vehiclearrow/NMSAccess.java

@@ -12,7 +12,7 @@ public class NMSAccess {
 
 	private Class<?> nmsArrowClass;
 
-	public void setupVehicleArrow() throws Exception {
+	public void setupVehicleArrow() throws NMSAccessException, ClassNotFoundException {
 		String pkgname = getClass().getPackage().getName();
 		String packageName = Bukkit.getServer().getClass().getPackage().getName();
 		String nmspackageversion = packageName.substring(packageName.lastIndexOf('.') + 1);
@@ -26,7 +26,7 @@ public class NMSAccess {
 				return;
 			}
 		}
-		throw new Exception("ChairsReloaded is not compatible with your server version");
+		throw new NMSAccessException("ChairsReloaded is not compatible with your server version");
 	}
 
 	public Arrow spawnArrow(Location location) throws NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {

src/com/cnaude/chairs/vehiclearrow/NMSAccessException.java

@@ -0,0 +1,11 @@
+package com.cnaude.chairs.vehiclearrow;
+
+public class NMSAccessException extends Exception {
+
+	private static final long serialVersionUID = -839103433400420225L;
+
+	public NMSAccessException(String message) {
+		super(message);
+	}
+
+}