NullPointerException in MDLV2000Reader

```
java.lang.NullPointerException: Cannot invoke "String.length()" because "line" is null
    at org.openscience.cdk.io.MDLV2000Reader.readAtomContainer(MDLV2000Reader.java:339)
    at org.openscience.cdk.io.MDLV2000Reader.readChemFile(MDLV2000Reader.java:260)
    at org.openscience.cdk.io.MDLV2000Reader.read(MDLV2000Reader.java:227)
```