multiple changes:

* refactor: improved target pointer init code and logic, added docs and runtime checks;
* game: fixed miss or wrong init calls in some continuous effects;
* game: fixed wrong usage of target pointers (miss copy code, miss npe checks);

Mage/src/main/java/mage/game/events/GameEvent.java

@@ -812,4 +812,9 @@ public class GameEvent implements Serializable {
     protected void setSourceId(UUID sourceId) {
         this.sourceId = sourceId;
     }
+
+    @Override
+    public String toString() {
+        return this.type.toString();
+    }
 }