PHPStan のエラーを修正

[nanasess]

------ ------------------------------------------------------------- 
 Line   class/pages/upgrade/LC_Page_Upgrade_Download.php             
------ ------------------------------------------------------------- 
 162    Variable $objRet in empty() always exists and is not falsy.  
------ ------------------------------------------------------------- 

------ ------------------------------------------------------------- 
 Line   class/pages/upgrade/LC_Page_Upgrade_ProductsList.php         
------ ------------------------------------------------------------- 
 116    Variable $objRet in empty() always exists and is not falsy.  
 176    Variable $objRet in empty() always exists and is not falsy.  
------ ------------------------------------------------------------- 

@return アノテーションの間違い

 ------ --------------------------------------------------------------- 
  Line   class/util/SC_Utils.php                                        
 ------ --------------------------------------------------------------- 
  1899   Variable $filename in empty() always exists and is not falsy.  
 ------ --------------------------------------------------------------- 

$filename は string|false なので empty() で評価できない

 ------ --------------------------------------------------------------- 
  Line   smarty_extends/function.html_checkboxes_ex.php                 
 ------ --------------------------------------------------------------- 
  105    Variable $values in isset() always exists and is always null.  
 ------ --------------------------------------------------------------- 

 ------ --------------------------------------------------------------- 
  Line   smarty_extends/function.html_radios_ex.php                     
 ------ --------------------------------------------------------------- 
  107    Variable $values in isset() always exists and is always null.  
 ------ --------------------------------------------------------------- 

エラーメッセージが変更されたため、ignoreErrors から漏れてしまった

[codecov-commenter]

Codecov Report

Merging #493 (1ed7795) into master (eb43f49) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master     #493   +/-   ##
=========================================
  Coverage     46.62%   46.62%           
  Complexity       14       14           
=========================================
  Files            81       81           
  Lines         10580    10580           
=========================================
  Hits           4933     4933           
  Misses         5647     5647           

Flag	Coverage Δ
tests	46.62% <100.00%> (ø)

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Impacted Files	Coverage Δ
data/class/util/SC_Utils.php	52.87% <100.00%> (ø)

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[nanasess]

Windows のホストランナーで mailcatcher がビルドできなくなり、 Docker も使用できなかったため削除しました