[DB-14827] Bug Fix: Migration Complexity Explanation empty in case of Oracle

[sanyamsinghal]

Describe the changes in this pull request

• updated html template to check for empty value

Describe if there are any user-facing changes

Only html report will change in oracle for this section.
There is no section for explanation as you can see below

How was this pull request tested?

Manually

Does your PR have changes that can cause upgrade issues?

Component	Breaking changes?
MetaDB	Yes/No
Name registry json	Yes/No
Data File Descriptor Json	Yes/No
Export Snapshot Status Json	Yes/No
Import Data State	Yes/No
Export Status Json	Yes/No
Data .sql files of tables	Yes/No
Export and import data queue	Yes/No
Schema Dump	Yes/No
AssessmentDB	Yes/No
Sizing DB	Yes/No
Migration Assessment Report Json	Yes/No
Callhome Json	Yes/No
YugabyteD Tables	Yes/No
TargetDB Metadata Tables	Yes/No

[makalaaneesh]

LGTM