hledger-flow: electrum: fix calculating 'No Data'

If electrum-provided prices aren't available, 'No Data' will be given.
Attempts to calculate this string will result in 0.00 for fiat values.

Do not attempt to calculate this string. Instead, leave the column empty
(for bitcoin.tax calculations).

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

@@ -52,11 +52,24 @@ function parse()
        value=$4-$6  # Remove fee
        printf("%.8f", value); printf OFS
 
-       sub(/^-/, "", $5)
-       printf("%.8f", $5); printf OFS  # fiat_value
+       # fiat_value
+       if ($5 !~ /^No Data$/)
+         {
+           sub(/^-/, "", $5)
+           printf("%.8f", $5)
+         }
+       printf OFS
 
-       printf("%.8f", $6); printf OFS  # fee
-       printf("%.8f", $7); printf OFS  # fiat_fee
+       # fee
+       printf("%.8f", $6)
+       printf OFS
+
+       # fiat_fee
+       if ($7 !~ /^No Data$/)
+         {
+           printf("%.8f", $7)
+         }
+       printf OFS
 
        # timestamp
        sub(/ /, "T", $8)  # HACK: makes arg-friendly by removing space