Add tolerance to nil response for error log

[stevenlanders]

Describe your changes and provide context

• If the broadcast request returns as nil response, the log statement would panic
• This makes the log statement tolerant to a nil response, causing a restart

Testing performed to validate your change

• Reproduced and added unit test

[codecov]

Codecov Report

Merging #1070 (a707c5c) into main (0895bcc) will decrease coverage by 0.06%.
The diff coverage is 73.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1070      +/-   ##
==========================================
- Coverage   63.63%   63.58%   -0.06%     
==========================================
  Files         256      256              
  Lines       16584    16593       +9     
==========================================
- Hits        10553    10550       -3     
- Misses       5529     5539      +10     
- Partials      502      504       +2     

Files	Coverage Δ
oracle/price-feeder/oracle/oracle.go	70.52% <73.33%> (+1.69%)	⬆️

... and 1 file with indirect coverage changes