[#8859] Check for sequences in generateSchemaIfEmpty()

The `JavaGenerator` should also generate Java code for schemas which
only contain sequences. This was missing in `generateSchemaIfEmpty()`.

jOOQ-codegen/src/main/java/org/jooq/codegen/JavaGenerator.java

@@ -427,6 +427,7 @@ private final boolean generateSchemaIfEmpty(SchemaDefinition schema) {
             && database.getEnums(schema).isEmpty()
             && database.getPackages(schema).isEmpty()
             && database.getRoutines(schema).isEmpty()
+            && database.getSequences(schema).isEmpty()
             && database.getTables(schema).isEmpty()
             && database.getUDTs(schema).isEmpty())
             return false;