Merge pull request #3304 from springfox/bugfix/model-enhancement

Check to prevent NPE. #3303

Author: dilipkrish

springfox-spring-web/src/main/java/springfox/documentation/spring/web/scanners/ApiModelReader.java

@@ -291,7 +291,7 @@ private Set<String> findSameModels(
       for (ModelReference modelReference : rootModel.getSubTypes()) {
         Optional<String> modelId = getModelId(modelReference);
 
-        if (modelId.isPresent()) {
+        if (modelId.isPresent() && mergingContext.containsModel(modelId.get())) {
           String sModelId = modelId.get();
           ModelContext modelContext = Optional.ofNullable(parametersMatching.get(sModelId))
               .map(op -> op.orElseGet(() -> parameter))
@@ -311,7 +311,7 @@ private Set<String> findSameModels(
         ModelReference modelReference = property.getModelRef();
         Optional<String> modelId = getModelId(modelReference);
 
-        if (modelId.isPresent()) {
+        if (modelId.isPresent() && mergingContext.containsModel(modelId.get())) {
           String sModelId = modelId.get();
           ModelContext modelContext = Optional.ofNullable(parametersMatching.get(sModelId))
               .map(op -> op.orElseGet(() -> parameter))