cannot set element to null in foreach

core/mapobjs/defobjs/Portal.java

@@ -82,6 +82,7 @@ public class Portal extends DefaultElement {
 	public boolean leave(Portal portal) {
 		if(portal.equals(this)) {
 			this.setFieldNeigboursBack();
+			this.otherSide = null;
 			this.getField().addToRemove(this);
 			return true;
 		}else {
@@ -90,11 +91,16 @@ public class Portal extends DefaultElement {
 
 	}
 
+	/**
+	 * Reset the linkage of Fields
+	 */
 	private void setFieldNeigboursBack()
 	{
+		if(otherSide != null) {
 			this.getField().getNeighbour(side).setNeighbour(Direction.convertToInverse(side), this.getField());
 			otherSide.getField().getNeighbour(otherSide.side).setNeighbour(Direction.convertToInverse(otherSide.side), otherSide.getField());
 		}
+	}
 
 
 

core/mapobjs/defobjs/Wall.java

@@ -72,9 +72,10 @@ public class Wall extends DefaultElement{
     {
     	if(portal == null)
     		return false;
-    	for (Portal myportal : this.portals) {
-    		if(portal.equals(myportal)) {
-    			myportal = null;
+    	for (int i = 0; i < portals.length; i++) {
+    		if(portal.equals(portals[i])) {
+    			System.out.println("falrol le");
+    			portals[i] = null;
 		}
     	}
         return false;