Remove custom InlineModelResolver

The custom InlineModelResolver is no longer needed as upstream project fixed it in swagger-api/swagger-codegen#9765 and released with version https://github.com/swagger-api/swagger-codegen/releases/tag/v2.4.9

plugin/src/main/java/com/yelp/codegen/SharedCodegen.kt

@@ -1,13 +1,13 @@
 package com.yelp.codegen
 
-import com.yelp.codegen.utils.InlineModelResolver
 import com.yelp.codegen.utils.safeSuffix
 import io.swagger.codegen.CodegenConfig
 import io.swagger.codegen.CodegenModel
 import io.swagger.codegen.CodegenOperation
 import io.swagger.codegen.CodegenProperty
 import io.swagger.codegen.CodegenType
 import io.swagger.codegen.DefaultCodegen
+import io.swagger.codegen.InlineModelResolver
 import io.swagger.codegen.SupportingFile
 import io.swagger.models.ArrayModel
 import io.swagger.models.ComposedModel
@@ -92,6 +92,7 @@ abstract class SharedCodegen : DefaultCodegen(), CodegenConfig {
 
     override fun preprocessSwagger(swagger: Swagger) {
         super.preprocessSwagger(swagger)
+        InlineModelResolver().flatten(swagger)
 
         unsafeOperations.addAll(when (val it = swagger.info.vendorExtensions["x-operation-ids-unsafe-to-use"]) {
             is List<*> -> it.filterIsInstance<String>()
@@ -119,8 +120,7 @@ abstract class SharedCodegen : DefaultCodegen(), CodegenConfig {
      * computing models names.
      */
     private fun mapXModel(swagger: Swagger) {
-        InlineModelResolver().flatten(swagger)
-        swagger.definitions.forEach { name, model ->
+        swagger.definitions?.forEach { (name, model) ->
             (model.vendorExtensions?.get(X_MODEL) as? String?)?.let { x_model ->
                 xModelMatches[name] = x_model
             }