Remove sub-stage from removed component

Fixes a bug where if you delete the parent component of a booster set, it would throw a NullPointerException in BarrowmanCalculator.java:861

core/src/net/sf/openrocket/rocketcomponent/FlightConfiguration.java

@@ -60,7 +60,7 @@ public class FlightConfiguration implements FlightConfigurableParameter<FlightCo
 	}
 	
 	/* Cached data */
-	final protected Map<Integer, StageFlags> stages = new HashMap<Integer, StageFlags>();
+	final protected Map<Integer, StageFlags> stages = new HashMap<Integer, StageFlags>();	// Map of stage number to StageFlags of the corresponding stage
 	final protected Map<MotorConfigurationId, MotorConfiguration> motors = new HashMap<MotorConfigurationId, MotorConfiguration>();
 	final private Collection<MotorConfiguration> activeMotors = new ArrayList<MotorConfiguration>();
 	final private InstanceMap activeInstances = new InstanceMap();

core/src/net/sf/openrocket/rocketcomponent/Rocket.java

@@ -748,6 +748,14 @@ public class Rocket extends ComponentAssembly {
         fireComponentChangeEvent(ComponentChangeEvent.TREE_CHANGE);
         return nextConfig.getFlightConfigurationID();
 	}
+
+	/**
+	 * Return all the flight configurations of this rocket.
+	 * @return all the flight configurations of this rocket.
+	 */
+	public FlightConfigurableParameterSet<FlightConfiguration> getFlightConfigurations() {
+		return this.configSet;
+	}
 	
 	
 	/**

core/src/net/sf/openrocket/rocketcomponent/RocketComponent.java

@@ -1545,6 +1545,11 @@ public abstract class RocketComponent implements ChangeSource, Cloneable, Iterab
 				AxialStage stage = (AxialStage) component;
 				this.getRocket().forgetStage(stage);
 			}
+
+			// Remove sub-stages of the removed component
+			for (AxialStage stage : component.getSubStages()) {
+				this.getRocket().forgetStage(stage);
+			}
 			
 			this.checkComponentStructure();
 			component.checkComponentStructure();