scsi: qla4xxx: Prevent a potential error pointer dereference

In the Linux kernel, the following vulnerability has been resolved: scsi: qla4xxx: Prevent a potential error pointer dereference The qla4xxx_get_ep_fwdb() function is supposed to return NULL on error, but qla4xxx_ep_connect() returns error pointers. Propagating the error pointers will lead to an Oops in the caller, so change the error pointers to NULL.