avoid computing alternative currency rate when no txs in history
avoid computing alternative currency rate when no txs in history

bitjson/copay,hideoussquid/aur-copay,troggy/colu-copay-wallet,cmgustavo/copay,jameswalpole/copay,kleetus/copay,willricketts/copay,gabrielbazan7/copay,JDonadio/copay,tanojaja/copay,Neurosploit/copay,ObsidianCryptoVault/copay,tanojaja/copay,payloadtech/wallet,startcoin-project/startwallet,ionux/copay,javierbitpay/copay,DigiByte-Team/copay,msalcala11/copay,cobit-wallet/cobit,Kirvx/copay,jmaurice/copay,Groestlcoin/GroestlPay,hideoussquid/aur-copay,mzpolini/copay,payloadpk/wallet,BitGo/copay,Neurosploit/copay,hideoussquid/aur-copay,mpolci/copay,mzpolini/copay,LedgerHQ/copay,bitjson/copay,CryptArc/platinumpay,troggy/unicoisa,LedgerHQ/copay,JDonadio/copay,Groestlcoin/GroestlPay,ionux/copay,urv2/wallet,kleetus/copay,jameswalpole/copay,MonetaryUnit/copay,jameswalpole/copay,ztalker/copay,wallclockbuilder/copay,solderzzc/copay,javierbitpay/copay,wyrdmantis/copay,habibmasuro/copay,MonetaryUnit/copay,fr34k8/copay,bitchk-wallet/copay,troggy/unicoisa,johnsmith76/Lite-Wallet,wyrdmantis/copay,hideoussquid/aur-copay,startcoin-project/startwallet,DigiByte-Team/copay,bitjson/copay,payloadtech/wallet,digibyte/digibytego,habibmasuro/copay,bitchk-wallet/copay,bankonme/copay,JDonadio/copay,troggy/copay,ajp8164/copay,DigiByte-Team/copay,mpolci/copay,wallclockbuilder/copay,payloadpk/wallet,javierbitpay/copay,wyrdmantis/copay,cmgustavo/copay,willricketts/copay,ztalker/copay,ztalker/copay,BitGo/copay,troggy/copay,ObsidianCryptoVault/copay,LedgerHQ/copay,javierbitpay/copay,Bitcoin-com/Wallet,philosodad/copay,mzpolini/copay,bankonme/copay,gabrielbazan7/copay,matiu/copay,Neurosploit/copay,troggy/copay,msalcala11/copay,johnsmith76/Lite-Wallet,troggy/colu-copay-wallet,urv2/wallet,julianromera/copay,BitGo/copay,startcoin-project/startwallet,troggy/unicoisa,isocolsky/copay,DigiByte-Team/copay,robjohnson189/copay,matiu/copay,troggy/unicoisa,tanojaja/copay,kleetus/copay,ObsidianCryptoVault/copay,troggy/colu-copay-wallet,Kirvx/copay,digibyte/digibytego,isocolsky/copay,CryptArc/platinumpay,jmaurice/copay,MonetaryUnit/copay,johnsmith76/Lite-Wallet,robjohnson189/copay,fr34k8/copay,mpolci/copay,isocolsky/copay,ztalker/copay,bechi/copay,fr34k8/copay,philosodad/copay,Kirvx/copay,ajp8164/copay,Tetpay/copay,solderzzc/copay,payloadtech/wallet,startcoin-project/startwallet,tanojaja/copay,JDonadio/copay,gabrielbazan7/copay,solderzzc/copay,ObsidianCryptoVault/copay,payloadpk/wallet,bechi/copay,CryptArc/platinumpay,dabura667/copay,mzpolini/copay,mpolci/copay,willricketts/copay,Bitcoin-com/Wallet,gabrielbazan7/copay,cmgustavo/copay,MonetaryUnit/copay,troggy/colu-copay-wallet,solderzzc/copay,Groestlcoin/GroestlPay,DigiByte-Team/copay,LedgerHQ/copay,payloadpk/wallet,cobit-wallet/cobit,ionux/copay,msalcala11/copay,bankonme/copay,wyrdmantis/copay,BitGo/copay,bechi/copay,fr34k8/copay,urv2/wallet,wallclockbuilder/copay,robjohnson189/copay,matiu/copay,robjohnson189/copay,Tetpay/copay,janko33bd/copay,msalcala11/copay,matiu/copay,dabura667/copay,Kirvx/copay,habibmasuro/copay,dabura667/copay,Bitcoin-com/Wallet,janko33bd/copay,philosodad/copay,payloadtech/wallet,johnsmith76/Lite-Wallet,philosodad/copay,DigiByte-Team/copay,janko33bd/copay,jameswalpole/copay,willricketts/copay,cobit-wallet/cobit,julianromera/copay,bitchk-wallet/copay,julianromera/copay,CryptArc/platinumpay,habibmasuro/copay,Bitcoin-com/Wallet,jmaurice/copay,wallclockbuilder/copay,jmaurice/copay,cmgustavo/copay,bitjson/copay,isocolsky/copay,urv2/wallet,troggy/copay,ajp8164/copay,ionux/copay,DigiByte-Team/copay,Groestlcoin/GroestlPay,Neurosploit/copay,bankonme/copay,julianromera/copay,kleetus/copay,digibyte/digibytego