[infrastructure] add external null-annotations (#8848)

Signed-off-by: Jan N. Klug <jan.n.klug@rub.de>

bundles/org.openhab.persistence.dynamodb/src/main/java/org/openhab/persistence/dynamodb/internal/DynamoDBPersistenceService.java

@@ -422,7 +422,7 @@ public class DynamoDBPersistenceService extends AbstractBufferedPersistenceServi
             String tableName = tableNameResolver.fromItem(dynamoItem);
             Deque<DynamoDBItem<?>> batch = batchesByTable.computeIfAbsent(tableName, new Function<>() {
                 @Override
-                public Deque<DynamoDBItem<?>> apply(String t) {
+                public Deque<DynamoDBItem<?>> apply(@Nullable String t) {
                     return new ArrayDeque<>();
                 }
             });