There is no error about "..balance does not have enough funds to pay gas.."
like this(screenshot is from another branch):

Instead of it, the user can "start" swap but will get an error(this branch):

Thanks for the catch - BTC should not have anything to do with gas! I'll revisit the logic and see where it went wrong.

@Canialon should be fixed now

On selecting coin with 0 balance in simple form as trade From, there're no error for it and infinite spinner on top of the form.

[13:14:48] [warning] [qt.trading.page.cpp:908] [4079]: last_trading_error is BalanceIsLessThanTheMinimalTradingAmount
[13:14:48] [info] [qt.orderbook.model.cpp:388] [4079]: full orderbook initialization initial size: 0 target size: 1, orderbook_kind: 1
[13:14:48] [info] [qt.orderbook.model.cpp:388] [4079]: full orderbook initialization initial size: 0 target size: 6, orderbook_kind: 2
[13:14:48] [info] [qt.orderbook.cpp:113] [4079]: selected best orders have a value - set preffered order
[13:14:48] [warning] [qt.trading.page.cpp:1473] [4079]: Spurious min_diff detected - (not) overriding immediately (using get_orderbook_wrapper()->get_current_min_taker_vol())

On selecting coin with 0 balance in simple form as trade From, there're no error for it and infinite spinner on top of the form.

[13:14:48] [warning] [qt.trading.page.cpp:908] [4079]: last_trading_error is BalanceIsLessThanTheMinimalTradingAmount
[13:14:48] [info] [qt.orderbook.model.cpp:388] [4079]: full orderbook initialization initial size: 0 target size: 1, orderbook_kind: 1
[13:14:48] [info] [qt.orderbook.model.cpp:388] [4079]: full orderbook initialization initial size: 0 target size: 6, orderbook_kind: 2
[13:14:48] [info] [qt.orderbook.cpp:113] [4079]: selected best orders have a value - set preffered order
[13:14:48] [warning] [qt.trading.page.cpp:1473] [4079]: Spurious min_diff detected - (not) overriding immediately (using get_orderbook_wrapper()->get_current_min_taker_vol())

Thanks for the feedback - should be fixed now.