[Python] Accidentally calling pyarrow.Table() should not segfault process

[asfimport]

While we need not go crazy with null-pointer checks, the code that gets executed by repr(pyarrow.Table()) should result in a more helpful error message

Reporter: Wes McKinney / @wesm
Assignee: Wes McKinney / @wesm

_{Note: This issue was originally created as ARROW-970. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
PR: #702

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 702
#702