fix #6096: bugfix for creating zero amount LN invoice
fix #6096: bugfix for creating zero amount LN invoice

(also there was a unit-mismatch here...)

wakiyamap/electrum-mona,vialectrum/vialectrum,spesmilo/electrum,pooler/electrum-ltc,wakiyamap/electrum-mona,wakiyamap/electrum-mona,pooler/electrum-ltc,pooler/electrum-ltc,vialectrum/vialectrum,spesmilo/electrum,spesmilo/electrum,vialectrum/vialectrum,wakiyamap/electrum-mona,spesmilo/electrum,pooler/electrum-ltc