Empty data in delete transactions event payload

[nagdahimanshu]

What was the problem?

This PR resolves #1958

How was it solved?

• Add null check before dispatching deleteTransactions signal
• Fix update.round event payload
• Update delay to 10s for blocks caching upon error

How was it tested?

Local

[codecov]

Codecov Report

Merging #1960 (67759ef) into development (02db4f1) will increase coverage by 0.04%.
Report is 7 commits behind head on development.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff               @@
##           development    #1960      +/-   ##
===============================================
+ Coverage        67.99%   68.03%   +0.04%     
===============================================
  Files              299      299              
  Lines             5305     5309       +4     
  Branches           977      978       +1     
===============================================
+ Hits              3607     3612       +5     
+ Misses            1698     1697       -1     

Files	Coverage Δ
...ndexer/shared/dataService/business/transactions.js	30.76% <ø> (+2.69%)	⬆️

... and 5 files with indirect coverage changes