Closes #1706 library(data.table) fails if "Packaged" field is not pre…

…sent in DESCRIPTION

alternate approach to this issue which avoids call to try()

R/onAttach.R

@@ -2,13 +2,17 @@
   # Runs when attached to search() path such as by library() or require()
   if (interactive()) {
     v = packageVersion("data.table")
-    d = try(read.dcf(system.file("DESCRIPTION", package="data.table"))[,"Packaged"])
-    if(inherits(d, "try-error")){
-      d = try(strsplit(read.dcf(system.file("DESCRIPTION", package="data.table"))[,"Built"], split="; ")$Built[3])
-      if(inherits(d, "try-error")){
-        return()
+    d = read.dcf(system.file("DESCRIPTION", package="data.table"), fields = c("Packaged", "Built"))
+    if(is.na(d[1])){
+      if(is.na(d[2])){
+        return() #neither field exists
+      } else{
+        d = unlist(strsplit(d[2], split="; "))[3]
       }
+    } else {
+      d = d[1]
     }
+
     dev = as.integer(v[1,3])%%2 == 1  # version number odd
     packageStartupMessage("data.table ", v, if(dev) paste0(" IN DEVELOPMENT built ", d))
     if (dev && (Sys.Date() - as.Date(d))>28) packageStartupMessage("**********\nThis development version of data.table was built more than 4 weeks ago. Please update.\n**********")