Make sure we don't eat all system memory

I had wrong configuration files, the encription algorithm definitely
doesn't take it into account.

core/device.cpp

@@ -57,6 +57,7 @@ Device::Device(QObject* parent, const QString& id)
     m_deviceName = info.deviceName;
     m_deviceType = str2type(info.deviceType);
     m_publicKey = QCA::RSAPublicKey::fromPEM(info.publicKey);
+    Q_ASSERT(m_publicKey.maximumEncryptSize(NetworkPackage::EncryptionAlgorithm)>0);
 
     m_pairingTimeut.setSingleShot(true);
     m_pairingTimeut.setInterval(30 * 1000);  //30 seconds of timeout

core/networkpackage.cpp

@@ -166,6 +166,7 @@ void NetworkPackage::encrypt(QCA::PublicKey& key)
     QByteArray serialized = serialize();
 
     int chunkSize = key.maximumEncryptSize(NetworkPackage::EncryptionAlgorithm);
+    Q_ASSERT(chunkSize>0);
 
     QStringList chunks;
     while (!serialized.isEmpty()) {