fhir_melt loses rows

[palmjulia]

When a indexed table has NA in the column that is used for melting, the corresponding row get's lost. This is not the case with current version on CRAN.

Example:

d <- data.table(id = c("[1]1", "[1]2"),
				melt_me = c("[1.1]a || [2.1]b", NA))

fhir_melt(d, columns = "melt_me", all_columns = TRUE, brackets = c("[", "]"), sep = " || ")

produces

     id melt_me resource_identifier
1: [1]1    [1]a                   1
2: [1]1    [1]b                   1