Fix #7 - Error upload might be deleted from rbtree
Fix #7 - Error upload might be deleted from rbtree

Due to the done flag not being correctly set to 0 when the error
tracker triggers, it could happen that such upload could be mistakenly
removed from the the rbtree that contains all in-flight uploads.
Thanks to Theo Cushion for finding this issue.

Signed-off-by: Brice Figureau <a6504fc3011a6983be6bf4d915860368a7353a38@daysofwonder.com>

gencer/nginx-upload-progress-module,gencer/nginx-upload-progress-module,masterzen/nginx-upload-progress-module,Tiger66639/nginx-upload-progress-module,perusio/nginx-upload-progress-module,Tiger66639/nginx-upload-progress-module,perusio/nginx-upload-progress-module,masterzen/nginx-upload-progress-module