files: don't check uninitialized memory when writing new file [valgrind]

This fixes https://savannah.gnu.org/bugs/?57934.

Bug existed since version 4.3, commit e8e30e51.

src/files.c

@@ -1701,7 +1701,7 @@ bool write_file(const char *name, FILE *thefile, bool tmp,
 		}
 	}
 
-	if (!tmp && S_ISFIFO(st.st_mode))
+	if (isactualfile && S_ISFIFO(st.st_mode))
 		statusbar(_("Writing to FIFO..."));
 #endif /* !NANO_TINY */