Fix stacktrace when fail_on_error is False and a file cannot be parsed. (#49987)

lib/ansible/modules/crypto/certificate_complete_chain.py

@@ -230,6 +230,7 @@ def load_PEM_list(module, path, fail_on_error=True):
             module.fail_json(msg=msg)
         else:
             module.warn(msg)
+            return []
 
 
 class CertificateSet(object):