Merge pull request #1587 from danieldietrich/fix-list-remove

NullPointer Exception could occur on equals call.

javaslang/src/main/java/javaslang/collection/List.java

@@ -1039,7 +1039,7 @@ default List<T> remove(T element) {
         boolean found = false;
         while (!found && !result.isEmpty()) {
             final T head = result.head();
-            if (head.equals(element)) {
+            if (Objects.equals(head, element)) {
                 found = true;
             } else {
                 preceding.addFirst(head);