Fix 'NoneType' object has no attribute error in bigquery_test.py

[ihji]

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[ihji]

R: @tvalentyn

[codecov]

Codecov Report

Merging #17746 (ca7a80f) into master (2d57753) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #17746      +/-   ##
==========================================
- Coverage   73.98%   73.98%   -0.01%     
==========================================
  Files         695      695              
  Lines       91774    91798      +24     
==========================================
+ Hits        67898    67914      +16     
- Misses      22627    22635       +8     
  Partials     1249     1249              

Flag	Coverage Δ
python	83.74% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
sdks/python/apache_beam/internal/gcp/auth.py	73.33% <0.00%> (-7.71%)	⬇️
sdks/python/apache_beam/utils/interactive_utils.py	95.12% <0.00%> (-2.44%)	⬇️
sdks/python/apache_beam/runners/direct/executor.py	96.46% <0.00%> (-0.55%)	⬇️
sdks/python/apache_beam/io/gcp/gcsio.py	92.26% <0.00%> (ø)
sdks/python/apache_beam/transforms/core.py	92.30% <0.00%> (ø)
...hon/apache_beam/runners/worker/bundle_processor.py	93.55% <0.00%> (ø)
...dks/python/apache_beam/options/pipeline_options.py	94.93% <0.00%> (+0.01%)	⬆️
...apache_beam/runners/dataflow/internal/apiclient.py	77.39% <0.00%> (+0.03%)	⬆️
sdks/python/apache_beam/io/gcp/gcsfilesystem.py	88.65% <0.00%> (+0.41%)	⬆️
sdks/python/apache_beam/coders/typecoders.py	93.67% <0.00%> (+1.26%)	⬆️
... and 1 more

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[chamikaramj]

LGTM. Thanks.