fix: vet actors shims

1. Check error in EraseAllUnproven
2. Avoid dead code.

chain/actors/builtin/miner/state.go.template

@@ -479,12 +479,15 @@ func (s *state{{.v}}) EraseAllUnproven() error {
 
 			return dls.UpdateDeadline(s.store, dindx, dl)
 		})
+		if err != nil {
+			return err
+		}
 
 		return s.State.SaveDeadlines(s.store, dls)
 	{{else}}
 		// field doesn't exist until v2
+                return nil
 	{{end}}
-	return nil
 }
 
 func (d *deadline{{.v}}) LoadPartition(idx uint64) (Partition, error) {

chain/actors/builtin/miner/v0.go

@@ -444,8 +444,8 @@ func (s *state0) decodeSectorPreCommitOnChainInfo(val *cbg.Deferred) (SectorPreC
 func (s *state0) EraseAllUnproven() error {
 
 	// field doesn't exist until v2
-
 	return nil
+
 }
 
 func (d *deadline0) LoadPartition(idx uint64) (Partition, error) {

chain/actors/builtin/miner/v2.go

@@ -470,10 +470,12 @@ func (s *state2) EraseAllUnproven() error {
 
 		return dls.UpdateDeadline(s.store, dindx, dl)
 	})
+	if err != nil {
+		return err
+	}
 
 	return s.State.SaveDeadlines(s.store, dls)
 
-	return nil
 }
 
 func (d *deadline2) LoadPartition(idx uint64) (Partition, error) {

chain/actors/builtin/miner/v3.go

@@ -467,10 +467,12 @@ func (s *state3) EraseAllUnproven() error {
 
 		return dls.UpdateDeadline(s.store, dindx, dl)
 	})
+	if err != nil {
+		return err
+	}
 
 	return s.State.SaveDeadlines(s.store, dls)
 
-	return nil
 }
 
 func (d *deadline3) LoadPartition(idx uint64) (Partition, error) {

chain/actors/builtin/miner/v4.go

@@ -467,10 +467,12 @@ func (s *state4) EraseAllUnproven() error {
 
 		return dls.UpdateDeadline(s.store, dindx, dl)
 	})
+	if err != nil {
+		return err
+	}
 
 	return s.State.SaveDeadlines(s.store, dls)
 
-	return nil
 }
 
 func (d *deadline4) LoadPartition(idx uint64) (Partition, error) {

chain/actors/builtin/miner/v5.go

@@ -467,10 +467,12 @@ func (s *state5) EraseAllUnproven() error {
 
 		return dls.UpdateDeadline(s.store, dindx, dl)
 	})
+	if err != nil {
+		return err
+	}
 
 	return s.State.SaveDeadlines(s.store, dls)
 
-	return nil
 }
 
 func (d *deadline5) LoadPartition(idx uint64) (Partition, error) {