TINKERPOP-3038: Console plugins file can't accept empty lines

[flora-jin]

TINKERPOP: https://issues.apache.org/jira/browse/TINKERPOP-3038

Added if statement in console.groovy to check for invalid plugins in plugins.txt (outputs invalid plugin and incorrect plugin name on console)
Added check to skip empty lines in plugins.txt on Mediator.groovy.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.

Project coverage is 76.36%. Comparing base (9b46b67) to head (260b018).
Report is 307 commits behind head on 3.7-dev.

Files with missing lines	Patch %	Lines
...rg/apache/tinkerpop/gremlin/console/Console.groovy	0.00%	6 Missing ⚠️
...g/apache/tinkerpop/gremlin/console/Mediator.groovy	0.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             3.7-dev    #3003      +/-   ##
=============================================
+ Coverage      76.14%   76.36%   +0.22%     
- Complexity     13152    13236      +84     
=============================================
  Files           1084     1061      -23     
  Lines          65160    61582    -3578     
  Branches        7285     7344      +59     
=============================================
- Hits           49616    47028    -2588     
+ Misses         12839    12036     -803     
+ Partials        2705     2518     -187     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[Cole-Greer]

Thanks for the bugfix @flora-jin. VOTE +1

[andreachild]

VOTE +1

[xiazcy]

Thanks for the bug fix! VOTE +1

[kenhuuu]

VOTE +1, pending CHANGELOG entry.