Kibana returns 500 when connected to incompatible ES version

[skearns64]

Kibana version: head of 5.1 branch

Elasticsearch version: 5.0.0

Server OS version: MacOS

Original install method (e.g. download page, yum, from source, etc.): tar.gz

Description of the problem including expected versus actual behavior:

I pointed Kibana 5.1.1 at an Elasticsearch 5.0 cluster. As expected, the logs have a nice message making the version compatibility issue clear. However, if you try to load Kibana in the browser, you get a 500 response, and an exception is printed in the logs:

Logs:

bin/kibana
  log   [14:41:56.352] [info][status][plugin:[email protected]] Status changed from uninitialized to green - Ready
  log   [14:41:56.407] [info][status][plugin:[email protected]] Status changed from uninitialized to yellow - Waiting for Elasticsearch
  log   [14:41:56.446] [info][status][plugin:[email protected]] Status changed from uninitialized to yellow - Waiting for Elasticsearch
  log   [14:41:56.606] [info][status][plugin:[email protected]] Status changed from uninitialized to yellow - Waiting for Elasticsearch
  log   [14:41:56.614] [info][status][plugin:[email protected]] Status changed from uninitialized to green - Ready
  log   [14:41:56.617] [warning][reporting] Generating a random key for xpack.reporting.encryptionKey. To prevent pending reports from failing on restart, please set xpack.reporting.encryptionKey in kibana.yml
  log   [14:41:56.622] [info][status][plugin:[email protected]] Status changed from uninitialized to yellow - Waiting for Elasticsearch
  log   [14:41:56.653] [info][status][plugin:[email protected]] Status changed from uninitialized to yellow - Waiting for Elasticsearch
  log   [14:41:56.654] [warning][security] Generating a random key for xpack.security.encryptionKey. To prevent sessions from being invalidated on restart, please set xpack.security.encryptionKey in kibana.yml
  log   [14:41:56.657] [warning][security] Session cookies will be transmitted over insecure connections. This is not recommended.
  log   [14:41:56.713] [info][status][plugin:[email protected]] Status changed from uninitialized to yellow - Waiting for Elasticsearch
  log   [14:41:56.735] [info][status][plugin:[email protected]] Status changed from uninitialized to green - Ready
  log   [14:41:56.920] [info][status][plugin:[email protected]] Status changed from uninitialized to green - Ready
  log   [14:41:56.927] [info][listening] Server running at http://localhost:5601
  log   [14:41:56.928] [info][status][ui settings] Status changed from uninitialized to yellow - Elasticsearch plugin is yellow
  log   [14:41:57.010] [error][status][plugin:[email protected]] Status changed from yellow to red - This version of Kibana requires Elasticsearch v5.1.1 on all nodes. I found the following incompatible nodes in your cluster: v5.0.1 @ 10.180.109.32:18411 (10.180.109.32)
  log   [14:41:57.011] [error][status][plugin:[email protected]] Status changed from yellow to red - This version of Kibana requires Elasticsearch v5.1.1 on all nodes. I found the following incompatible nodes in your cluster: v5.0.1 @ 10.180.109.32:18411 (10.180.109.32)
  log   [14:41:57.012] [error][status][plugin:[email protected]] Status changed from yellow to red - This version of Kibana requires Elasticsearch v5.1.1 on all nodes. I found the following incompatible nodes in your cluster: v5.0.1 @ 10.180.109.32:18411 (10.180.109.32)
  log   [14:41:57.012] [error][status][plugin:[email protected]] Status changed from yellow to red - This version of Kibana requires Elasticsearch v5.1.1 on all nodes. I found the following incompatible nodes in your cluster: v5.0.1 @ 10.180.109.32:18411 (10.180.109.32)
  log   [14:41:57.013] [error][status][plugin:[email protected]] Status changed from yellow to red - This version of Kibana requires Elasticsearch v5.1.1 on all nodes. I found the following incompatible nodes in your cluster: v5.0.1 @ 10.180.109.32:18411 (10.180.109.32)
  log   [14:41:57.013] [error][status][plugin:[email protected]] Status changed from yellow to red - This version of Kibana requires Elasticsearch v5.1.1 on all nodes. I found the following incompatible nodes in your cluster: v5.0.1 @ 10.180.109.32:18411 (10.180.109.32)
  log   [14:41:57.015] [error][status][ui settings] Status changed from yellow to red - Elasticsearch plugin is red
 error  [14:42:06.304]  TypeError: Cannot read property 'toJSON' of undefined
    at replaceInjectedVars$ (/skearns/es/kibana-5.1.1-darwin-x86_64/plugins/x-pack/plugins/xpack_main/server/lib/replace_injected_vars.js:10:53)
    at tryCatch (/skearns/es/kibana-5.1.1-darwin-x86_64/node_modules/regenerator/runtime.js:61:40)
    at GeneratorFunctionPrototype.invoke [as _invoke] (/skearns/es/kibana-5.1.1-darwin-x86_64/node_modules/regenerator/runtime.js:323:22)
    at GeneratorFunctionPrototype.prototype.(anonymous function) [as next] (/skearns/es/kibana-5.1.1-darwin-x86_64/node_modules/regenerator/runtime.js:94:21)
    at GeneratorFunctionPrototype.invoke (/skearns/es/kibana-5.1.1-darwin-x86_64/node_modules/regenerator/runtime.js:132:37)
 error  [14:42:20.970]  TypeError: Cannot read property 'toJSON' of undefined
    at replaceInjectedVars$ (/skearns/es/kibana-5.1.1-darwin-x86_64/plugins/x-pack/plugins/xpack_main/server/lib/replace_injected_vars.js:10:53)
    at tryCatch (/skearns/es/kibana-5.1.1-darwin-x86_64/node_modules/regenerator/runtime.js:61:40)
    at GeneratorFunctionPrototype.invoke [as _invoke] (/skearns/es/kibana-5.1.1-darwin-x86_64/node_modules/regenerator/runtime.js:323:22)
    at GeneratorFunctionPrototype.prototype.(anonymous function) [as next] (/skearns/es/kibana-5.1.1-darwin-x86_64/node_modules/regenerator/runtime.js:94:21)
    at GeneratorFunctionPrototype.invoke (/skearns/es/kibana-5.1.1-darwin-x86_64/node_modules/regenerator/runtime.js:132:37)

In the browser: shows the following JSON:

{"statusCode":500,"error":"Internal Server Error","message":"An internal server error occurred"}

Steps to reproduce:

1. With x-pack installed, configure elasticsearch.url (and username/password) to point at ES 5.0 cluster