Fix errorhandling for reading from a pipe

When reading a line from a pipe failed on no data being read, the
errorhandling was erroneously logging with %m even thoug no error
description is available for %m to print.  This flaw accidentally
introduced in 5c7038d.

Reported-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/baa34329-f431-46af-bf74-1a78fdc90e4f@eisentraut.org

Author: danielgustafsson

src/common/exec.c

@@ -393,8 +393,8 @@ pipe_read_line(char *cmd)
 			log_error(errcode_for_file_access(),
 					  _("could not read from command \"%s\": %m"), cmd);
 		else
-			log_error(errcode_for_file_access(),
-					  _("no data was returned by command \"%s\": %m"), cmd);
+			log_error(errcode(ERRCODE_NO_DATA),
+					  _("no data was returned by command \"%s\""), cmd);
 	}
 
 	(void) pclose_check(pipe_cmd);