Save stats when stats file is empty

[btror]

when the stats file is completely empty and you do a test the results are not saved and you get this:

raijq: error: syntax error, unexpected '[', expecting FORMAT or QQSTRING_START (Unix shell quoting issues?) at , line 3:
.average.["tests taken"] += 1 | jq: error: syntax error, unexpected ')', expecting $end (Unix shell quoting issues?) at , line 4:
.average.wpm = ((.average.wpm * (.average.["test taken"] - 1) + $new_wpm) / .average.["tests taken"]) |
jq: 2 compile errors
mkdir: : No such file or directory

temporary solution is to add empty {} brackets in stats.json to start with