Merge pull request #929 from swagger-api/codegen-issues-11049

fixed NPE on spring generator when using discriminator mapping

Author: HugoMario

src/main/java/io/swagger/codegen/v3/generators/java/SpringCodegen.java

@@ -876,6 +876,11 @@ protected List<Map<String, Object>> modelInheritanceSupport(List<?> allModels) {
             Map<String, Object> parent = new HashMap<>();
             parent.put("classname", parentModel.classname);
             List<CodegenModel> childrenModels = byParent.get(parentModel);
+
+            if (childrenModels == null || childrenModels.isEmpty()) {
+                continue;
+            }
+
             for (CodegenModel model : childrenModels) {
                 Map<String, Object> child = new HashMap<>();
                 child.put("name", model.name);