A ConcurrentHashMap does not work with null keys or values. This mean…

…s it will crash when you call ConcurrentHashMap.getOrDefault(null).

We were calling ConcurrentHashMap.getOrDefault(userId), and userId was nullable in that context.

Fixed logic to prevent ConcurrentHashMap.getOrDefault method being called with null input.

src/main/java/uk/gov/companieshouse/accounts/association/mapper/AssociationsListMappers.java

@@ -43,7 +43,11 @@ public AssociationsList daoToDto( final Page<AssociationDao> associationsList, f
         final var endpointUrl = computeEndpointUrl( companyDetails );
         final var users = Objects.isNull( userDetails ) ? usersService.fetchUserDetails( associationsList.stream() ) : Map.of( userDetails.getUserId(), userDetails );
         final var companies = Objects.isNull( companyDetails ) ? companyService.fetchCompanyProfiles( associationsList.stream() ) : Map.of( companyDetails.getCompanyNumber(), companyDetails );
-        final var associations = associationsList.map( associationDao -> daoToDto( associationDao, users.getOrDefault( associationDao.getUserId(), null ), companies.get( associationDao.getCompanyNumber() ) ) );
+        final var associations = associationsList.map( associationDao -> {
+            final var user = Objects.isNull( associationDao.getUserId() ) ? null : users.getOrDefault( associationDao.getUserId(), null );
+            final var company = companies.get( associationDao.getCompanyNumber() );
+            return daoToDto( associationDao, user, company );
+        } );
         return enrichWithMetadata( associations, endpointUrl );
     }