controllers/sample_set.py: skip a result_file when we cannot link it to a sample

see #4536
7 jobs for feature-s/4536-robust-qc-stats in 13 minutes and 52 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test Tools
passed #850078
test_tools

00:00:10

 
  Test Quality
passed #850079
code_quality

00:03:03

 
  Test Unit
passed #850080
web
test_server_unit

00:00:29

 
  Deploy Review
passed #850081
deploy_review_server

00:02:20

manual #850082
allowed to fail manual
stop_deploy_review_server
 
  Test Functional
passed #850083
docker x86_64
ff32-server-functional

00:07:58

passed #850084
docker x86_64
ff45-server-functional

00:07:45