[Cherry-Pick]Fix error with Restic backup empty volumes

[qiuming-best]

Signed-off-by: Ming mqiu@vmware.com

Thank you for contributing to Velero!

Please add a summary of your change

Does your change fix a particular issue?

Fixes #(issue)
#5678
Fix error with Restic backup empty volumes

Please indicate you've done the following:

• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• Updated the corresponding documentation in site/content/docs/main.

[codecov-commenter]

Codecov Report

Merging #5713 (3b903e6) into main (55873c1) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main    #5713   +/-   ##
=======================================
  Coverage   40.92%   40.92%           
=======================================
  Files         239      239           
  Lines       20630    20630           
=======================================
  Hits         8442     8442           
  Misses      11571    11571           
  Partials      617      617           

Impacted Files	Coverage Δ
pkg/uploader/provider/restic.go	26.04% <0.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.