Fix NullPointerException in Jacoco coverage report merge logic (#9803)

Author: nikita-tkachenko-datadog

dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/coverage/report/JacocoCoverageProcessor.java

@@ -445,6 +445,11 @@ private long mergeAndUploadCoverageReport(IBundleCoverage coverageBundle) {
           continue;
         }
 
+        if (pathRelativeToIndexRoot == null) {
+          LOGGER.debug("Could not resolve source for path {}", pathRelativeToSourceRoot);
+          continue;
+        }
+
         LinesCoverage linesCoverage = getLinesCoverage(sourceFile);
         // backendCoverageData contains data for all modules in the repo,
         // but coverageBundle bundle only has source files that are relevant for the given module,