Fix leak in VPathRenderer

The pointer to the root group in the VPathRenderer is not freed anywhere
in the Java side so we need to take care of it on the "native" side.

Change-Id: I2ca60b1f0e975a0b5d29799c5f6f31b5f8d42b9d
(cherry picked from commit ffdb1b241d9458196403c8f16264aa7053487323)
3 files changed