Fixed exceptions when removing values that don't exist from bi-maps

src/dorkbox/util/collections/LockFreeIntBiMap.java

@@ -300,7 +300,9 @@ class LockFreeIntBiMap<V> {
     public synchronized
     V remove(final int key) {
         V value = forwardHashMap.remove(key);
+        if (value != null) {
             reverseHashMap.remove(value, defaultReturnValue);
+        }
         return value;
     }
 

src/dorkbox/util/collections/LockFreeObjectIntBiMap.java

@@ -276,7 +276,9 @@ class LockFreeObjectIntBiMap<V> {
     public synchronized
     int remove(final V key) {
         int value = forwardHashMap.remove(key, defaultReturnValue);
+        if (value != defaultReturnValue) {
             reverseHashMap.remove(value);
+        }
         return value;
     }