When you try and spend more of a `FungibleAsset` than you have available, you receive the following error message:
FlowException("Insufficient balance, missing $amountMissing")
This does not differentiate between the following two cases:
The node has sufficient funds, but some of the funds are soft-locked
The node has insufficient funds, even considering soft-locked funds
This is important in some cases. For example, suppose a UI where a user has $10 and tries to transfer $6 to a counterparty. If they accidentally click the button twice, the flow may be started twice, and they will see the exception above. It will not be clear to them that the failure was because they tried to start the same flow twice in quick succession.