[#51] *: Do not panic in StableSize()

After #49 it can be called on nil structures.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

netmap/marshal.go

@@ -65,6 +65,10 @@ func (f *Filter) StableMarshal(buf []byte) []byte {
 }
 
 func (f *Filter) StableSize() (size int) {
+	if f == nil {
+		return 0
+	}
+
 	size += protoutil.StringSize(nameFilterField, f.name)
 	size += protoutil.StringSize(keyFilterField, f.key)
 	size += protoutil.EnumSize(opFilterField, int32(f.op))
@@ -101,6 +105,10 @@ func (s *Selector) StableMarshal(buf []byte) []byte {
 }
 
 func (s *Selector) StableSize() (size int) {
+	if s == nil {
+		return 0
+	}
+
 	size += protoutil.StringSize(nameSelectorField, s.name)
 	size += protoutil.UInt32Size(countSelectorField, s.count)
 	size += protoutil.EnumSize(countSelectorField, int32(s.clause))
@@ -132,6 +140,10 @@ func (r *Replica) StableMarshal(buf []byte) []byte {
 }
 
 func (r *Replica) StableSize() (size int) {
+	if r == nil {
+		return 0
+	}
+
 	size += protoutil.UInt32Size(countReplicaField, r.count)
 	size += protoutil.StringSize(selectorReplicaField, r.selector)
 
@@ -173,6 +185,10 @@ func (p *PlacementPolicy) StableMarshal(buf []byte) []byte {
 }
 
 func (p *PlacementPolicy) StableSize() (size int) {
+	if p == nil {
+		return 0
+	}
+
 	for i := range p.replicas {
 		size += protoutil.NestedStructureSize(replicasPolicyField, &p.replicas[i])
 	}

status/marshal.go

@@ -30,6 +30,10 @@ func (x *Detail) StableMarshal(buf []byte) []byte {
 }
 
 func (x *Detail) StableSize() (size int) {
+	if x == nil {
+		return 0
+	}
+
 	size += protoutil.UInt32Size(detailIDFNum, x.id)
 	size += protoutil.BytesSize(detailValueFNum, x.val)