odb_loose: only close file descriptor if it was opened successfully

src/odb_loose.c

@@ -433,7 +433,8 @@ static int read_header_loose(git_rawobj *out, git_buf *loc)
 	}
 
 done:
-	p_close(fd);
+	if (fd >= 0)
+		p_close(fd);
 	return error;
 }