Codec2Client: avoid a null pointer deref

Not 100% sure of the correctness of this fix, since I'm not super
familiar with this codebase; the static analyzer flagged `*syncObj`
below as a potential nullptr dereference, since we check for its
nullness below.

Bug: 157111613
Test: TreeHugger
Change-Id: I14817e97a70bf9ce0275885483a719bb1d0b4975