Bug with boolean indexing on empty DataFrame
xref http://stackoverflow.com/questions/12700251/pandas-edge-case-on-boolean-index-into-empty-dataframe

```
blah = pandas.DataFrame(numpy.empty([0, 1]), columns=['A'], index=pandas.DatetimeIndex([]))
blah[numpy.array([], bool)]
```

Empty DataFrame

```
blah[numpy.array([], bool)] = 0.0
```
