Validated the scenario on following 4.5 build & able to navigate back to pipeline list on cancelling new request with sidebar open. No exception or white screen observed.
OpenShift Version: 4.5.0-0.nightly-2020-07-23-023500
Kubernetes Version: v1.18.3+012b3ec
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.