Trying to request dav endpoint with POST request gives 500 Internal Server Error

[phil-davis]

See issue owncloud/core#38378

Sending no Content-Type in a POST can result in a 500 "internal server error" with traceback like:

Exception: explode() expects parameter 2 to be string, null given: {
\"Exception\":\"TypeError\",\"Message\":\"explode() expects parameter 2 to be string, null given\",\"Code\":0,\"Trace\":\"
#0 \\/home\\/dipakacharya\\/www\\/core\\/lib\\/composer\\/sabre\\/dav\\/lib\\/DAV\\/Browser\\/Plugin.php(160): explode()

If the Content-Type is not specified (null) then the explode() explodes!

[phil-davis]

Fixed by #1325
And fixes owncloud/core issue owncloud/core#38378