HDDS-11023. Recon Disk Usage null conditions not handled properly for…

[smitajoshi12]

What changes were proposed in this pull request?

To avoid null conditions on Disk Usage page

Please describe your PR in detail:

When Recon was intializing on Disk Usage page we were getting failures as values are not mapped properly so to avoid such conditions added checks.

What is the link to the Apache JIRA

(https://issues.apache.org/jira/browse/HDDS-11023)

How was this patch tested?

Manually

Before this PR

With this Patch