1 files changed, 4 insertions, 0 deletions

diff --git a/src/ch/epfl/xblast/Lists.java b/src/ch/epfl/xblast/Lists.java
index 7e3ba5e..9bd527b 100644
--- a/src/ch/epfl/xblast/Lists.java
+++ b/src/ch/epfl/xblast/Lists.java
@@ -250,6 +250,8 @@ public final class Lists {
      */
     public static <K, IK, V> Map<K, V> traverseMaps(Map<K, IK> m1, Map<IK, V> m2) {
         return Collections.unmodifiableMap(m1.entrySet().stream()
+                .filter(e -> Objects.nonNull(e.getValue()))
+                .filter(e -> Objects.nonNull(m2.get(e.getValue())))
                 .collect(Collectors.toMap(Map.Entry::getKey, e -> m2.get(e.getValue()))));
     }
 
@@ -263,6 +265,8 @@ public final class Lists {
      */
     public static <K, V> Map<K, V> invertMap(Map<V, K> m) {
         return Collections.unmodifiableMap(m.entrySet().stream()
+                .filter(e -> Objects.nonNull(e.getKey()))
+                .filter(e -> Objects.nonNull(e.getValue()))
                 .collect(Collectors.toMap(Map.Entry::getValue, Map.Entry::getKey)));
     }