Added in empty catch for json_decode

[caleuanhopkins]

Lumen and possible other setups are not having their JSON content decoded in the Symfony request. This is an attempt to capture any missed content from Symfony's request->all() method and prepare it for Botman to carry on delivering the response

[codecov]

Codecov Report

Merging #19 into master will decrease coverage by 0.04%.
The diff coverage is 50%.

@@             Coverage Diff              @@
##             master      #19      +/-   ##
============================================
- Coverage     53.48%   53.44%   -0.05%     
- Complexity       50       52       +2     
============================================
  Files             5        5              
  Lines           172      174       +2     
============================================
+ Hits             92       93       +1     
- Misses           80       81       +1

Impacted Files	Coverage Δ	Complexity Δ
src/WebDriver.php	74.4% <50%> (-0.4%)	45 <0> (+2)

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[caleuanhopkins]

Not the same problem but similar and covers details about the root of the issue that spawned this PR: botman/botman#807