fix(general): Reject exceptions with empty type and value

[jan-auer]

Fixes SENTRY-96G

[codecov-io]

Codecov Report

Merging #170 into master will increase coverage by 0.05%.
The diff coverage is 87.87%.

@@            Coverage Diff            @@
##           master    #170      +/-   ##
=========================================
+ Coverage   63.85%   63.9%   +0.05%     
=========================================
  Files          82      82              
  Lines        8792    8814      +22     
=========================================
+ Hits         5614    5633      +19     
- Misses       3178    3181       +3

Impacted Files	Coverage Δ
general/src/protocol/exception.rs	97.82% <100%> (+2.7%)	⬆️
general/src/store/normalize/contexts.rs	92.14% <100%> (ø)	⬆️
general/src/store/normalize.rs	92.59% <100%> (+0.12%)	⬆️
general/src/store/normalize/stacktrace.rs	100% <100%> (ø)	⬆️
general/src/types/impls.rs	80.86% <50%> (-0.55%)	⬇️

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