Don't display interest rate if profit is zero

It will end up showing very small and actually wrong numbers like
5.38939837311e-11 % or even -1.48880395563e-11 % if it's newly funded
wallet with no coinjoins happened yet.

jmclient/jmclient/wallet_utils.py

@@ -727,7 +727,10 @@ def wallet_fetch_history(wallet, options):
         now = jm_single().bc_interface.rpc('getblock', [bestblockhash])['time']
     print('     %s best block is %s' % (datetime.fromtimestamp(now)
         .strftime("%Y-%m-%d %H:%M"), bestblockhash))
-    print('total profit = ' + str(float(balance - sum(deposits)) / float(100000000)) + ' BTC')
+    total_profit = float(balance - sum(deposits)) / float(100000000)
+    print('total profit = ' + str(total_profit) + ' BTC')
+
+    if abs(total_profit) > 0:
         try:
             # https://gist.github.com/chris-belcher/647da261ce718fc8ca10
             import numpy as np