KDE-open is not installed on Gnome systems by default
Haveno tries to use `kde-open` when popping up a "Insufficient funds" message. kde-open is not installed on Gnome systems by deault. 

Ideally, there's a more universal way to do this; or try and detect that we're using a Gnome system and use the equivalent command.


Log file:
```
Jul-26 08:31:04.445 [JavaFX Application Thread] INFO  h.d.c.c.c.PopOver: hide:200.0 ms 
Jul-26 08:31:13.542 [JavaFX Application Thread] INFO  h.d.c.c.c.PopOver: hide:200.0 ms 
Jul-26 08:31:23.374 [JavaFX Application Thread] INFO  h.c.o.CreateOfferService: create and get offer with offerId=JKDLDJ-d2ff01de-4617-4120-8af9-174123ceda6b-109, currencyCode=EUR, direction=SELL, fixedPrice=null, useMarketBasedPrice=true, marketPriceMargin=0.001, amount=2939200000000, minAmount=752600000000, securityDeposit=0.15 
Jul-26 08:31:24.502 [OpenOfferManager] INFO  h.c.o.OpenOfferManager: Adding open offer JKDLDJ-d2ff01de-4617-4120-8af9-174123ceda6b-109 
Jul-26 08:31:24.503 [Thread-6638] WARN  h.c.o.OpenOfferManager: Unable to split or schedule funds for offer JKDLDJ-d2ff01de-4617-4120-8af9-174123ceda6b-109: Not enough funds to schedule offer 
Jul-26 08:31:24.503 [Thread-6638] WARN  h.c.o.OpenOfferManager: Error processing pending offer JKDLDJ-d2ff01de-4617-4120-8af9-174123ceda6b-109: Not enough funds to schedule offer 
Jul-26 08:31:24.503 [Thread-6638] INFO  h.c.o.OpenOfferManager: Removing open offer JKDLDJ-d2ff01de-4617-4120-8af9-174123ceda6b-109 
Jul-26 08:31:24.503 [Thread-6638] INFO  h.c.t.ClosedTradableManager: checking closed trades eligibility for having sensitive data cleared 
Jul-26 08:31:24.503 [Thread-6638] INFO  h.c.x.w.XmrWalletService: resetAddressEntriesForOpenOffer offerId=JKDLDJ-d2ff01de-4617-4120-8af9-174123ceda6b-109 
Jul-26 08:31:24.503 [Thread-6638] INFO  h.c.x.w.XmrWalletService: swap addressEntry with address 85HPL7NGMU1fNdBwngjdNr8BWSrjHUsd9jJNjj56j8DsTSr7cpmvTwMYPnCkJW5dHyYbWWG2hn8CFjFbTbM1SQEDPC4myeh and offerId JKDLDJ-d2ff01de-4617-4120-8af9-174123ceda6b-109 from context OFFER_FUNDING to available 
Jul-26 08:31:39.767 [JavaFX Application Thread] INFO  h.c.u.DesktopUtil: Trying to exec: cmd = kde-open args = %s file = /home/<snip>/.local/share/Haveno-reto/haveno.log 
Jul-26 08:31:39.769 [JavaFX Application Thread] WARN  h.c.u.DesktopUtil: Error running command. java.io.IOException: Cannot run program "kde-open": error=2, No such file or directory 
Jul-26 08:31:39.769 [JavaFX Application Thread] INFO  h.c.u.DesktopUtil: Trying to exec: cmd = gnome-open args = %s file = /home/cayle/.local/share/Haveno-reto/haveno.log 
Jul-26 08:31:39.771 [JavaFX Application Thread] WARN  h.c.u.DesktopUtil: Error running command. java.io.IOException: Cannot run program "gnome-open": error=2, No such file or directory 
<snip>
Jul-26 08:31:39.776 [JavaFX Application Thread] INFO  h.c.u.DesktopUtil: Process is running. 
```