qcacmn: Fix kw issue in target_if_reg.c

Pointer wmi_handle is returned from a function may
be NULL and will be dereferenced in another function.
Add sanity checking to return if the pointer is NULL.

Change-Id: I2a38098335dde8d76a04129c06166203aefdd2ec
CRs-Fixed: 2317021
1 file changed