fix: PackageUpdater failure

[PROFeNoM]

Description

In #3062, IntegrationTestCase was updated to declare getAppIndexScript and getConsoleScript. Since these methods now exist on any test suite extending IntegrationTestCase, we had this type of failures:

- Error processing /home/circleci/app/tests/Integrations/AMQP/Latest/AMQPTest.php: dirname(): Argument #1 ($path) must be of type string, null given
#0 /home/circleci/app/tests/PackageUpdater.php(94): dirname(NULL)
#1 /home/circleci/app/tests/PackageUpdater.php(66): PackageUpdater->findComposerFile('DDTrace\\Tests\\I...', '/home/circleci/...')
#2 /home/circleci/app/tests/PackageUpdater.php(21): PackageUpdater->processFile('/home/circleci/...')
#3 /home/circleci/app/tests/PackageUpdater.php(185): PackageUpdater->run()
#4 {main}

This fix just proposes to check whether it's null + exit 1 when errors are encountered.

Reviewer checklist

• Test coverage seems ok.
• Appropriate labels assigned.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.74%. Comparing base (c199419) to head (8427e87).

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #3078       +/-   ##
=============================================
+ Coverage     51.86%   74.74%   +22.87%     
  Complexity     2790     2790               
=============================================
  Files           112      112               
  Lines         11042    11042               
=============================================
+ Hits           5727     8253     +2526     
+ Misses         5315     2789     -2526     

Flag	Coverage Δ
tracer-php	74.74% <ø> (+22.87%)	⬆️

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see 20 files with indirect coverage changes

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[bwoebi]

Sounds good :-)