config: check for EOF before newline

If a line ends at EOF there is no need to check for the newline
character and doing so will cause us to read memory beyond the
allocatd memory as we check for the Windows-style new-line, which is
two bytes long.

Signed-off-by: Carlos Martín Nieto <cmn@elego.de>

src/config.c

@@ -537,12 +537,13 @@ static char *cfg_readline(git_config *cfg)
 	line_src = cfg->reader.read_ptr;
     line_end = strchr(line_src, '\n');
 
-	while (is_linebreak(line_end))
-		line_end = strchr(line_end + 1, '\n');
-
     /* no newline at EOF */
 	if (line_end == NULL)
 		line_end = strchr(line_src, 0);
+	else
+		while (is_linebreak(line_end))
+			line_end = strchr(line_end + 1, '\n');
+
 
 	while (line_src < line_end && isspace(*line_src))
 		line_src++;