DataFrame.append with empty list raises IndexError

[joaoe]

Code Sample

>>> import pandas
>>> pandas.DataFrame().append([])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File ".env\lib\site-packages\pandas\core\frame.py", line 7108, in append
    elif isinstance(other, list) and not isinstance(other[0], DataFrame):
IndexError: list index out of range
>>> pandas.__version__
'0.25.1'

Problem description

Crash when passing empty sequence to DataFrame.append

Expected Output

No crash.
The source DataFrame is returned intact.

Version

Version 0.25.1. Happens in master.
Problem line
https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L7014

[jbrockmendel]

What output are you hoping to see here? Still an empty DataFrame?

[joaoe]

I guess the source DataFrame() is expected since an empty sequence is just empty and there is nothing to append.

Like this

pandas.DataFrame({"a":[1,2]}).append([pandas.DataFrame()])

[jbrockmendel]

Seems reasonable. A PR would be welcome.