Issues with file upload and antivirus plugin

Description

Details at https://community.mattermost.com/core/pl/xsdtk7ymzpbife5u6bkoc493so

hey chris, we're using your antivirus plugin at UTC so thanks so much for offering it! quick question: we were just redeploying it in a 5.9 environment. It seems to work catching the test virus file, but we get an odd error:
{"level":"warn","ts":1553814843.1319351,"caller":"app/plugin_api.go:659","msg":"Virus found in file.","plugin_id":"antivirus","filename":"eicar.test","user":"c343m413g3n1xruspfs8amjr3a","scan_result":"stream: Eicar-Test-Signature FOUND"}
{"level":"error","ts":1553814843.2795095,"caller":"web/context.go:52","msg":"Unable to upload file(s). Error reading or parsing request data.","path":"/api/v4/files","request_id":"miejbobtxb8aznzxo3icob16hw","ip_addr":"10.192.164.188","user_id":"c343m413g3n1xruspfs8amjr3a","method":"POST","err_where":"uploadFileTask","http_code":400,"err_details":"Virus found in file."}
{"level":"info","ts":1553814856.8359334,"caller":"scheduler/worker.go:78","msg":"Worker: Job is complete","worker":"Plugins","job_id":"7c3maxtobf8ytgt917uenuguwr"}

QA Test Steps

Status

Mana

None

Assignee

Lev Brouk

QA Assignee

Dylan Haussermann

Reporter

Lev Brouk

Epic Link

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Fix versions

Mattermost Team

Integrations

Sprint

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GitHub Issue

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