UBIFS: check return code of pnode_lookup
UBIFS: check return code of pnode_lookup

Function pnode_lookup may return ERR_PTR(...). Check for it.

Signed-off-by: Vasiliy Kulikov <bf62e7c380ff4449c5c3c5c39150b7660ee28ecb@gmail.com>
Signed-off-by: Artem Bityutskiy <19b5733dcea388885746d36043d3568bba5b4df7@nokia.com>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs