src/Pure/General/file.scala

--- a/src/Pure/General/file.scala	Fri Mar 27 13:04:15 2020 +0100
+++ b/src/Pure/General/file.scala	Fri Mar 27 22:01:27 2020 +0100
@@ -213,7 +213,7 @@
     val line =
       try { reader.readLine}
       catch { case _: IOException => null }
-    if (line == null) None else Some(line)
+    Option(line)
   }
 
   def read_lines(reader: BufferedReader, progress: String => Unit): List[String] =