listbox autopaging does not work with external paginal

if autopaging is enabled with external paginal, an client error is thrown:

Uncaught TypeError: Cannot read property 'getTotalSize' of undefined
at _fixPageSize (zul.mesh.wpd:286)
at init._onRender (zul.mesh.wpd:1043)
at init._onRender (zk.wpd:38249)
at zk.wpd:11606

fix -> getTotalSize() should be retrieved following
(wgt.paging || wgt._paginal).getTotalSize();