fix not found element exception

Author: erwan-serandour

src/main/java/org/sonarqube/gradle/SonarQubePlugin.java

@@ -120,15 +120,17 @@ private static List<File> registerAndConfigureResolverTasks(Project topLevelProj
           if (sourceSets == null) {
             return null;
           }
-          return sourceSets.getByName(SourceSet.MAIN_SOURCE_SET_NAME).getCompileClasspath();
+          var set = sourceSets.findByName(SourceSet.MAIN_SOURCE_SET_NAME);
+          return set == null ? null : set.getCompileClasspath();
         });
         task.setCompileClasspath(compile);
         Provider<FileCollection> test = target.provider(() -> {
           var sourceSets = SonarUtils.getSourceSets(target);
           if (sourceSets == null) {
             return null;
           }
-          return sourceSets.getByName(SourceSet.TEST_SOURCE_SET_NAME).getCompileClasspath();
+          var set = sourceSets.findByName(SourceSet.TEST_SOURCE_SET_NAME);
+          return set == null ? null : set.getCompileClasspath();
         });
         task.setTestCompileClasspath(test);