Check for not string instead of None

[MichaelSquires]

• Instead of checking for None, validate the incoming storm text is a str type.

Updates SYN-5750

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.11% ⚠️

Comparison is base (e566ed9) 97.32% compared to head (d17a5c9) 97.21%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3269      +/-   ##
==========================================
- Coverage   97.32%   97.21%   -0.11%     
==========================================
  Files         227      227              
  Lines       45430    45430              
==========================================
- Hits        44214    44166      -48     
- Misses       1216     1264      +48     

Flag	Coverage Δ
linux	97.21% <100.00%> (ø)
linux_replay	?

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Files Changed	Coverage Δ
synapse/lib/view.py	97.10% <100.00%> (-0.33%)	⬇️

... and 9 files with indirect coverage changes

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