fixed crash if incorrect blinded signature type

libi2pd/LeaseSet.cpp

@@ -912,6 +912,11 @@ namespace data
 		uint8_t blindedPriv[64], blindedPub[128]; // 64 and 128 max
 		size_t publicKeyLen = blindedKey.BlindPrivateKey (keys.GetSigningPrivateKey (), date, blindedPriv, blindedPub);
 		std::unique_ptr<i2p::crypto::Signer> blindedSigner (i2p::data::PrivateKeys::CreateSigner (blindedKey.GetBlindedSigType (), blindedPriv));
+		if (!blindedSigner)
+		{
+			LogPrint (eLogError, "LeaseSet2: Can't create blinded signer for signature type ", blindedKey.GetSigType ());
+			return;
+		}	
 		auto offset = 1;
 		htobe16buf (m_Buffer + offset, blindedKey.GetBlindedSigType ()); offset += 2; // Blinded Public Key Sig Type
 		memcpy (m_Buffer + offset, blindedPub, publicKeyLen); offset += publicKeyLen; // Blinded Public Key