hledger-flow: coinbase: preprocess: fix Advanced Trade divide by zero

container/src/hledger-flow/accounts/coinbase/coinbase-shared.bash

@@ -144,12 +144,26 @@ function __parse()
        #
        # Add new columns to calculate fees against native currency price
        #
-       #  - 0 is used because Coinbase does not accurately display fiat amount,
-       #    if satoshi is small (valued less than $0.00)
+       # WARNING:
+       #
+       #  - `amount_amount` and/or `native_amount_amount` may be given as 0
+       #    because Coinbase does not display the full value of either column
+       #    for token values (satoshi, gwei, etc.) valued less than a $0.00.
+       #
+       #    Quite literally, the only value information that Coinbase will
+       #    provide for these transactions is 0 or equivalent; so, an accurate
+       #    calculation cannot be made nor inferred because the only other
+       #    usable information is the fee. But, since it is unknown what
+       #    percentage the fee-tier is for these transactions, no further
+       #    calculations can be made.
+       #
+       #    With that said, any 0-value transactions should skip the following
+       #    calculations as to avoid a divide by zero error and, instead, be
+       #    managed within the rules file.
        #
 
-       if ($7 > 0) {printf("%.8f", $7 / $5)}; printf OFS           # native_amount_price
-       if ($7 > 0) {printf("%.8f", ($7 / $5) * $16)}; printf OFS   # native_network_transaction_fee_amount
+       if ($7 > 0 && $5 > 0) {printf("%.8f", $7 / $5)}; printf OFS           # native_amount_price
+       if ($7 > 0 && $5 > 0) {printf("%.8f", ($7 / $5) * $16)}; printf OFS   # native_network_transaction_fee_amount
 
        #
        # Add new column to calculate the difference between amount and network fee,