Bug 540325: [RJ-Dbg] Fix ArrayIndexOutOfBoundsException

Change-Id: I3d730b1d8f69dd95b3612519c5fc742b8d137f84
diff --git a/core/org.eclipse.statet.rj.server/src/org/eclipse/statet/rj/server/dbg/TracepointPosition.java b/core/org.eclipse.statet.rj.server/src/org/eclipse/statet/rj/server/dbg/TracepointPosition.java
index d2f9a55..ef3d17d 100644
--- a/core/org.eclipse.statet.rj.server/src/org/eclipse/statet/rj/server/dbg/TracepointPosition.java
+++ b/core/org.eclipse.statet.rj.server/src/org/eclipse/statet/rj/server/dbg/TracepointPosition.java
@@ -101,7 +101,9 @@
 	}
 	
 	public int @Nullable [] getSrcref() {
-		return this.exprSrcrefs[this.exprSrcrefs.length - 1];
+		return (this.exprSrcrefs.length > 0) ?
+				this.exprSrcrefs[this.exprSrcrefs.length - 1] :
+				null;
 	}