fix(subscription-verifier): Totals is not always present in result

[lynnagara]

Not all subscriptions have "totals". Previously the verifier would
crash when it encountered a subscription without this key.

[codecov-commenter]

Codecov Report

Merging #2594 (fce669e) into master (4c356b3) will not change coverage.
The diff coverage is n/a.

❗ Current head fce669e differs from pull request most recent head 929824a. Consider uploading reports for the commit 929824a to get more accurate results

@@           Coverage Diff           @@
##           master    #2594   +/-   ##
=======================================
  Coverage   92.92%   92.92%           
=======================================
  Files         606      606           
  Lines       28126    28126           
=======================================
  Hits        26135    26135           
  Misses       1991     1991           

Impacted Files	Coverage Δ
snuba/subscriptions/verifier.py	76.13% <ø> (ø)

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