fix [Kotlin]: handle nullable response.body in jvm-okhttp ApiClient template (#23515)

Signed-off-by: Oyvind Mo <oymo76@gmail.com>

Author: oymo

modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiClient.kt.mustache

@@ -340,7 +340,7 @@ import com.squareup.moshi.adapter
     @OptIn(ExperimentalStdlibApi::class)
     {{/moshi}}
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JSON_MEDIA_TYPE): T? {
-        val body = response.body
+        val body = response.body ?: return null
 
         if (T::class.java == Unit::class.java) {
             // No need to parse the body when we're not interested in the body

samples/client/echo_api/kotlin-jvm-okhttp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -285,7 +285,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
 
     @OptIn(ExperimentalStdlibApi::class)
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JSON_MEDIA_TYPE): T? {
-        val body = response.body
+        val body = response.body ?: return null
 
         if (T::class.java == Unit::class.java) {
             // No need to parse the body when we're not interested in the body

samples/client/others/kotlin-integer-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -285,7 +285,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
 
     @OptIn(ExperimentalStdlibApi::class)
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JSON_MEDIA_TYPE): T? {
-        val body = response.body
+        val body = response.body ?: return null
 
         if (T::class.java == Unit::class.java) {
             // No need to parse the body when we're not interested in the body

samples/client/others/kotlin-jvm-okhttp-non-ascii-headers/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -285,7 +285,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
 
     @OptIn(ExperimentalStdlibApi::class)
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JSON_MEDIA_TYPE): T? {
-        val body = response.body
+        val body = response.body ?: return null
 
         if (T::class.java == Unit::class.java) {
             // No need to parse the body when we're not interested in the body

samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -285,7 +285,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
 
     @OptIn(ExperimentalStdlibApi::class)
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JSON_MEDIA_TYPE): T? {
-        val body = response.body
+        val body = response.body ?: return null
 
         if (T::class.java == Unit::class.java) {
             // No need to parse the body when we're not interested in the body

samples/client/others/kotlin-jvm-okhttp-path-comments/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -285,7 +285,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
 
     @OptIn(ExperimentalStdlibApi::class)
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JSON_MEDIA_TYPE): T? {
-        val body = response.body
+        val body = response.body ?: return null
 
         if (T::class.java == Unit::class.java) {
             // No need to parse the body when we're not interested in the body

samples/client/petstore/kotlin-allOf-discriminator-kotlinx-serialization/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -287,7 +287,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         }
 
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JSON_MEDIA_TYPE): T? {
-        val body = response.body
+        val body = response.body ?: return null
 
         if (T::class.java == Unit::class.java) {
             // No need to parse the body when we're not interested in the body

samples/client/petstore/kotlin-allOf-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -285,7 +285,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
 
     @OptIn(ExperimentalStdlibApi::class)
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JSON_MEDIA_TYPE): T? {
-        val body = response.body
+        val body = response.body ?: return null
 
         if (T::class.java == Unit::class.java) {
             // No need to parse the body when we're not interested in the body

samples/client/petstore/kotlin-array-integer-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -285,7 +285,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
 
     @OptIn(ExperimentalStdlibApi::class)
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JSON_MEDIA_TYPE): T? {
-        val body = response.body
+        val body = response.body ?: return null
 
         if (T::class.java == Unit::class.java) {
             // No need to parse the body when we're not interested in the body

samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -285,7 +285,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
 
     @OptIn(ExperimentalStdlibApi::class)
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JSON_MEDIA_TYPE): T? {
-        val body = response.body
+        val body = response.body ?: return null
 
         if (T::class.java == Unit::class.java) {
             // No need to parse the body when we're not interested in the body