Check if the data is null when get platform arn

[jun06t]

I sometimes get following error.

TypeError Cannot read property 'EndpointArn' of null 
    /usr/local/parse/node_modules/parse-server-sns-adapter/src/SNSPushAdapter.js:176:21 getPlatformArn
    /usr/local/parse/node_modules/parse-server-sns-adapter/node_modules/aws-sdk/lib/request.js:354:18 none
    /usr/local/parse/node_modules/parse-server-sns-adapter/node_modules/aws-sdk/lib/sequential_executor.js:105:20 callListeners
    /usr/local/parse/node_modules/parse-server-sns-adapter/node_modules/aws-sdk/lib/sequential_executor.js:77:10 emit
    /usr/local/parse/node_modules/parse-server-sns-adapter/node_modules/aws-sdk/lib/request.js:596:14 emit
    /usr/local/parse/node_modules/parse-server-sns-adapter/node_modules/aws-sdk/lib/request.js:21:10 transition
    /usr/local/parse/node_modules/parse-server-sns-adapter/node_modules/aws-sdk/lib/state_machine.js:14:12 runTo

to prevent this i fixed the code.

[rogerhu]

Do you happen to have a test you could add?

[jun06t]

i'm sorry. i've added a test.

[rogerhu]

Lgtm thanks