also check head commit message before using it

Author: daniel-mohedano

dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/config/ExecutionSettingsFactoryImpl.java

@@ -396,7 +396,8 @@ private Map<TestSetting, Map<String, Collection<TestFQN>>> getTestManagementTest
       return Collections.emptyMap();
     }
     try {
-      if (Strings.isNotBlank(pullRequestInfo.getGitCommitHead().getSha())) {
+      if (Strings.isNotBlank(pullRequestInfo.getGitCommitHead().getSha())
+          && Strings.isNotBlank(pullRequestInfo.getGitCommitHead().getFullMessage())) {
         return configurationApi.getTestManagementTestsByModule(
             tracerEnvironment,
             pullRequestInfo.getGitCommitHead().getSha(),