on delete client, check that the apiSpec have defined an oauth manager (

TykTechnologies#2944)

as reported in TykTechnologies#2940 on delete oauth client first we must check that the ApiSpec have a valid oauthManager loaded, in order to do so was added a validation to check that `apiSpec.OAuthManager` is not null

gateway/api.go

@@ -1876,25 +1876,29 @@ func handleDeleteOAuthClient(keyName, apiID string) (interface{}, int) {
 		return apiError("OAuth Client ID not found"), http.StatusNotFound
 	}
 
-	err := apiSpec.OAuthManager.OsinServer.Storage.DeleteClient(storageID, apiSpec.OrgID, true)
-	if err != nil {
-		return apiError("Delete failed"), http.StatusInternalServerError
-	}
+	if apiSpec.OAuthManager != nil{
+		err := apiSpec.OAuthManager.OsinServer.Storage.DeleteClient(storageID,apiSpec.OrgID, true)
+		if err != nil {
+			return apiError("Delete failed"), http.StatusInternalServerError
+		}
 
-	statusObj := apiModifyKeySuccess{
-		Key:    keyName,
-		Status: "ok",
-		Action: "deleted",
-	}
+		statusObj := apiModifyKeySuccess{
+			Key:    keyName,
+			Status: "ok",
+			Action: "deleted",
+		}
 
-	log.WithFields(logrus.Fields{
-		"prefix": "api",
-		"apiID":  apiID,
-		"status": "ok",
-		"client": keyName,
-	}).Info("Deleted OAuth client")
+		log.WithFields(logrus.Fields{
+			"prefix": "api",
+			"apiID":  apiID,
+			"status": "ok",
+			"client": keyName,
+		}).Info("Deleted OAuth client")
 
-	return statusObj, http.StatusOK
+		return statusObj, http.StatusOK
+	}
+
+	return apiError("OAuth Client ID not found"), http.StatusNotFound
 }
 
 const oAuthNotPropagatedErr = "OAuth client list isn't available or hasn't been propagated yet."