For the error on line 920, you can change the line:
$element->characteristics[$k]->default=end($mainCharacteristics[$element->product_id][$k]);
by:
if(!empty($mainCharacteristics[$element->product_id][$k])) $element->characteristics[$k]->default=end($mainCharacteristics[$element->product_id][$k]);
in the file administrator\components\com_hikashop\classes\cart.php
For the error on line 92, you can change the code:
foreach($rate->shipping_params->methods as $method){
if($method=='TDCB' || $method=='TDA' || $method=='TDO' || $method=='308' || $method=='309' || $method=='310'){
$this->freight=true;
}
else{
$this->classicMethod=true;
}
}
by the code:
if(!empty($rate->shipping_params->methods)){
foreach($rate->shipping_params->methods as $method){
if($method=='TDCB' || $method=='TDA' || $method=='TDO' || $method=='308' || $method=='309' || $method=='310'){
$this->freight=true;
}
else{
$this->classicMethod=true;
}
}
}
in the file plugins\hikashopshipping\ups\ups.php