Warning messages - clean up

[leppott]

Is your feature request related to a problem? Please describe.
Clean up warning messages when have missing columns for metrics. The first warning is ok. The 2nd is a product of the first (All NA fields go to logical class). The 2nd is an issue with classes of columns and reshape2::melt.

Describe the solution you'd like
Probably check for an "logical" fields and convert to numeric before use reshape2::melt in metric.values function.

Describe alternatives you've considered
NA

Additional context

[leppott]

Should be easy enough to avoid the 2nd message by checking for any all NA columns and convert the data type. Then should not get the 2nd warning message.