Add tracking target parameter

source/Model/CtrlObject.ts

@@ -61,8 +61,8 @@ class CtrlObject extends LabelObject {
     /**
      * 判断是否为相同对象
      */
-    public equal(obj: CtrlObject): boolean {
-        return this === obj || this.id === obj.id;
+    public equal(obj?: CtrlObject): boolean {
+        return this === obj || this.id === obj?.id;
     }
 
     /**

source/Model/Group.ts

@@ -272,9 +272,11 @@ class Group extends CtrlObject {
     public remove(individual: Individual[] | Individual): this {
         if (Array.isArray(individual)) {
             for (let i = 0; i < individual.length; i++) {
+                individual[i].group = undefined;
                 this.individuals.delete(individual[i]);
             }
         } else {
+            individual.group = undefined;
             this.individuals.delete(individual);
         }
         return this;

source/Model/Individual.ts

@@ -88,7 +88,7 @@ class Individual {
 	/**
 	 * 所属群组
 	 */
-	public group: Group;
+	public group: Group | undefined;
 
 	/**
 	 * 初始化
@@ -97,11 +97,16 @@ class Individual {
 		this.group = group;
 	}
 
+    public isDie(): boolean {
+        return !!this.group;
+    }
+
     /**
      * 死亡
      */
     public die(): this {
-        this.group.remove(this);
+        this.group?.remove(this);
+        this.group = undefined;
         return this;
     }
 
@@ -110,7 +115,7 @@ class Individual {
      * @param newGroup 新群体
      */
     public transfer(newGroup: Group): this {
-        this.group.remove(this);
+        this.group?.remove(this);
         newGroup.add(this);
         this.group = newGroup;
         return this;