lang: funcs: Avoid erroneous empty message in readfile

Readfile had a bug where it sent an empty string on startup. This has
ben fixed, and it now waits until the file contents are ready before
sending a string.

lang/funcs/core/os/readfile_func.go

@@ -164,6 +164,7 @@ func (obj *ReadFileFunc) Stream() error {
 					//err = nil // reset
 				}
 			}()
+			continue // wait for an actual event or we'd send empty!
 
 		case err, ok := <-obj.events:
 			if !ok {