Index Error
Hi, I get the following error:
`Error: unhandled exception: index 171115068 not in 0 .. 171115067 [IndexError]`

With the following bed file:
```
4	2576604	3576604
X	66265159	67265159
6	15827865	16827865
12	111536754	112536754
14	92037355	93037355
19	12818673	13818673
3	63398361	64398361
6	170370995	171370995
12	6545880	7545880
16	87137889	88137889
X	146493555	147493555
X	147082159	148082159
19	45773463	46773463
9	71152201	72152201
3	128391420	129391420
9	27073483	28073483
20	2133379	3133379
22	45691235	46691235
21	44696324	45696324
5	145758291	151258291
13	70213516	71213516
1	57332716	58332716
8	118879055	119879055
18	52753385	53753385
14	23290682	24290682
X	24531771	25531771
```

But when I run with a similar bed file, everything works:
```
4	3026604	3126770	HD
X	66715159	66815360	SBMA
6	16277865	16378050	SCA1
12	111986754	112086950	SCA2
14	92487355	92587555	SCA3
19	13268673	13368873	SCA6
3	63848361	63948561	SCA7
6	170820995	170921200	SCA17
12	6995880	7096100	DRPLA
16	87587899	87688100	HDL2
X	146943555	147043755	FRAXA
X	147532159	147632359	FRAXE
19	46223463	46323663	DM1
9	71602201	71702401	FRDA
3	128841420	128941620	DM2
9	27523483	27623683	FTDALS1
20	2583379	2683579	SCA36
22	46141235	46241435	SCA10
21	45146324	45246524	EPM1
5	146208291	146308491	SCA12
13	70663516	70763716	SCA8
16	66474302	66574502	SCA31
1	57782716	57882916	SCA37
8	119329055	119429255	FAME1
18	53203385	53303585	FECD3
14	23740682	23840682	OPMD
X	24981771	25081971	EIEE1
```

I have tried to figure out if there are any errors in the first bed file, but I can't find any.
Both bed files are tab-separated. 

What could cause an Index Error?


Thanks for the help. 