A PHP Warning is triggered if an empty array is passed to node_view_multiple().
Documentation says that node_view_multiple() accepts "An array of nodes as returned by node_load_multiple()."
So, node_view_multiple() should be able to use any node_load_multiple() result without any kind of
conditional statements... But node_load_multiple() could return an empty array, which is not correctly used in node_view_multiple(), resulting with the following PHP Warning :
Warning: uasort() expects parameter 1 to be array, null given in node_view_multiple() (line 2679 of /modules/node/node.module).