examples not build successfully

[egraldlo]

hi,

   I use maven to build the spark0.7.2, and I successfully build spark-core,streaming,bagel. But when building spark-examples, it comes out a error that 

"[error] failed to execute goal net".alchim31.maven:scala-maven-plugin:3.1.0:compile (scala-compile-first) on project spark-examples_2.9.3: Execution scala-compile-first of goal net.alchim31.maven:scala-maven-plugin:3.1.0:compile failed: For artifact {null:null:null:jar}: The groupId cannot be empty. -> [Help 1]"

and the spark-examples building failed. who met with this situation and I hope can get some help