ausplots_visual with few plots

[GregGuerin]

ausplots_visual calls with 1 of small number of plots in some cases crashes, particularly in relation to fractional cover calculations - can't find field names, which suggests the table is dropping out in some cases.

[GregGuerin]

Problem was with few plots if there were no NA fraction hits the table from frat_cover would not have a column called NA and it was looking for it to make the pie - solved by calling for cols 2:ncol instead of naming bare brown green NA in PIE