Changing line 38 to try and fix build

Odd Jenkins build failures even though command-line build works fine:

```
:rxjava:rxjava-contrib:rxjava-debug:compileJava/mnt/builds/slave/workspace/OSS-RxJava-release/rxjava-contrib/rxjava-debug/src/main/java/rx/plugins/DebugNotification.java:38: ')' expected
            sourceFunc = ((DebugHook<C>.DebugOnSubscribe<T>) sourceFunc).getActual();
                                       ^
/mnt/builds/slave/workspace/OSS-RxJava-release/rxjava-contrib/rxjava-debug/src/main/java/rx/plugins/DebugNotification.java:38: ')' expected
            sourceFunc = ((DebugHook<C>.DebugOnSubscribe<T>) sourceFunc).getActual();
                                        ^
/mnt/builds/slave/workspace/OSS-RxJava-release/rxjava-contrib/rxjava-debug/src/main/java/rx/plugins/DebugNotification.java:38: illegal start of expression
            sourceFunc = ((DebugHook<C>.DebugOnSubscribe<T>) sourceFunc).getActual();
                                                           ^
/mnt/builds/slave/workspace/OSS-RxJava-release/rxjava-contrib/rxjava-debug/src/main/java/rx/plugins/DebugNotification.java:38: not a statement
            sourceFunc = ((DebugHook<C>.DebugOnSubscribe<T>) sourceFunc).getActual();
                                                             ^
/mnt/builds/slave/workspace/OSS-RxJava-release/rxjava-contrib/rxjava-debug/src/main/java/rx/plugins/DebugNotification.java:38: ';' expected
            sourceFunc = ((DebugHook<C>.DebugOnSubscribe<T>) sourceFunc).getActual();
                                                                       ^
5 errors
 FAILED
```