Fixed whisper pub key bug

* Unrecoverable messages would cause segfault when recovering invalid
  pub key

crypto/crypto.go

@@ -92,7 +92,7 @@ func ToECDSAPub(pub []byte) *ecdsa.PublicKey {
 }
 
 func FromECDSAPub(pub *ecdsa.PublicKey) []byte {
-	if pub == nil {
+	if pub == nil || pub.X == nil || pub.Y == nil {
 		return nil
 	}
 	return elliptic.Marshal(S256(), pub.X, pub.Y)

whisper/whisper.go

@@ -197,7 +197,7 @@ func (self *Whisper) add(envelope *Envelope) error {
 		go self.postEvent(envelope)
 	}
 
-	wlogger.DebugDetailln("added whisper message")
+	wlogger.DebugDetailf("added whisper envelope %x\n", envelope)
 
 	return nil
 }