proto detect - fix coverity CID 1204325

CID 1204325 (#1 of 1): Logically dead code (DEADCODE)
dead_error_line: Execution cannot reach this statement: mask = 0U;.
433        mask = 0;

additionally, mask is initialized to 0

src/app-layer-detect-proto.c

@@ -437,8 +437,6 @@ static AppProto AppLayerProtoDetectPPGetProto(Flow *f,
         mask = pp_port_dp->alproto_mask;
     else if (pp_port_sp)
         mask = pp_port_sp->alproto_mask;
-    else
-        mask = 0;
 
     if (alproto_masks[0] == mask) {
         FLOW_SET_PP_DONE(f, direction);