Android: Use isValid() to check if the jobject is valid.
Android: Use isValid() to check if the jobject is valid.

Change-Id: I5ec67b9b2abfae2e2c2a44f0bcc7c72cb54beb49
Reviewed-by: Yoann Lopes <27570619e45a2a46618012b16a29b452c478e806@digia.com>

mer-qt/qtmultimedia,mer-qt/qtmultimedia,mer-qt/qtmultimedia,mer-qt/qtmultimedia,mer-qt/qtmultimedia