Query result with zero rows returns data.frame without columns

[david-cortes]

Steps to reproduce:

• Establish a connection to some DB
• Run a query that would not return any rows, but which would anyway have defined columns, e.g.

  con <- RPostgreSQL::dbConnect(DBI::dbDriver("PostgreSQL"), dbname = dbname,
                                host = host, port = 5432,
                                user = user, password = password)
  RPostgreSQL::dbGetQuery(con, "select 'a' as col1, 'b' as col2 where false")

Expected results: Should return a data.frame with zero rows and the column names that would be specified by the query.

Actual results: Returns an empty data.frame with zero rows and zero columns.

[drkarthi]

92 seems to be a potential fix