nimble/l2cap: Fix use on uninitialized value
nimble/l2cap: Fix use on uninitialized value

X-Original-Commit: 60cf149ff041ffced8b0729928fa17149b2a72a8

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble