avoid error when testing for membership in a nonexistent directory

Author: ianfixes

Diff for: CHANGELOG.md

@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
 - Don't define `ostream& operator<<(nullptr_t)` if already defined by Apple
+- `CppLibrary.in_tests_dir?` no longer produces an error if there is no tests directory
 
 ### Security
 

Diff for: lib/arduino_ci/cpp_library.rb

@@ -122,6 +122,8 @@ def vendor_bundle?(path)
     # @param path [Pathname] The path to check
     # @return [bool]
     def in_tests_dir?(path)
+      return false unless tests_dir.exist?
+
       tests_dir_aliases = [tests_dir, tests_dir.realpath]
       # we could do this but some rubies don't return an enumerator for ascend
       # path.ascend.any? { |part| tests_dir_aliases.include?(part) }