Exception when building the project with empty source code files

One of our module had an empty source code file (actually someone just commented everything in that file). Maven was able to build the project but sonar crashed with following error:
...
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] Can not execute Sonar

[INFO] ------------------------------------------------------------------------
[DEBUG] Trace
org.apache.maven.lifecycle.LifecycleExecutionException: Can not execute Sonar
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:564)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeStandaloneGoal(DefaultLifecycleExecutor.java:493)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:463)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:311)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:224)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:143)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:333)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:126)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:282)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
at org.codehaus.classworlds.Launcher.main(Launcher.java:375)
Caused by: org.apache.maven.plugin.MojoExecutionException: Can not execute Sonar
at org.codehaus.mojo.sonar.Bootstraper.executeMojo(Bootstraper.java:87)
at org.codehaus.mojo.sonar.Bootstraper.start(Bootstraper.java:65)
at org.codehaus.mojo.sonar.SonarMojo.execute(SonarMojo.java:117)
at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:447)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:539)
... 16 more
Caused by: java.util.NoSuchElementException
at java.util.TreeMap.key(TreeMap.java:433)
at java.util.TreeMap.firstKey(TreeMap.java:287)
at java.util.TreeSet.first(TreeSet.java:407)
at org.sonar.squid.entities.Resource.getFirstChild(Resource.java:65)
at org.sonar.plugins.squid.SquidMavenCollector.collectFileMeasures(SquidMavenCollector.java:141)
at org.sonar.plugins.squid.SquidMavenCollector.collect(SquidMavenCollector.java:89)
at org.sonar.mojo.InternalMojo.executeCollectors(InternalMojo.java:294)
at org.sonar.mojo.InternalMojo.processModules(InternalMojo.java:176)
at org.sonar.mojo.InternalMojo.execute(InternalMojo.java:160)
at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:447)
at org.codehaus.mojo.sonar.Bootstraper.executeMojo(Bootstraper.java:82)
... 20 more

Work sound is to remove the file.