// taken from http://www.hunlock.com/blogs/Totally_Pwn_CSS_with_Javascript

function getCSSRule(ruleName, deleteFlag) {               // Return requested style obejct
   ruleName=ruleName.toLowerCase();                       // Convert test string to lower case.
   if (document.styleSheets) {                            // If browser can play with stylesheets
      for (var i=0; i<document.styleSheets.length; i++) { // For each stylesheet
         var styleSheet=document.styleSheets[i];          // Get the current Stylesheet
         var ii=0;                                        // Initialize subCounter.
         var cssRule=false;                               // Initialize cssRule. 
         do {                                             // For each rule in stylesheet
            if (styleSheet.cssRules) {                    // Browser uses cssRules?
               cssRule = styleSheet.cssRules[ii];         // Yes --Mozilla Style
            } else {                                      // Browser usses rules?
               cssRule = styleSheet.rules[ii];            // Yes IE style. 
            }                                             // End IE check.
            if (cssRule)  {                               // If we found a rule...
               if (cssRule.selectorText.toLowerCase()==ruleName) { //  match ruleName?
                  if (deleteFlag=='delete') {             // Yes.  Are we deleteing?
                     if (styleSheet.cssRules) {           // Yes, deleting...
                        styleSheet.deleteRule(ii);        // Delete rule, Moz Style
                     } else {                             // Still deleting.
                        styleSheet.removeRule(ii);        // Delete rule IE style.
                     }                                    // End IE check.
                     return true;                         // return true, class deleted.
                  } else {                                // found and not deleting.
                     return cssRule;                      // return the style object.
                  }                                       // End delete Check
               }                                          // End found rule name
            }                                             // end found cssRule
            ii++;                                         // Increment sub-counter
         } while (cssRule)                                // end While loop
      }                                                   // end For loop
   }                                                      // end styleSheet ability check
   return false;                                          // we found NOTHING!
}                                                         // end getCSSRule 

function killCSSRule(ruleName) {                          // Delete a CSS rule   
   return getCSSRule(ruleName,'delete');                  // just call getCSSRule w/delete flag.
}                                                         // end killCSSRule

function addCSSRule(ruleName) {                           // Create a new css rule
   if (document.styleSheets) {                            // Can browser do styleSheets?
      if (!getCSSRule(ruleName)) {                        // if rule doesn't exist...
         if (document.styleSheets[0].addRule) {           // Browser is IE?
            document.styleSheets[0].addRule(ruleName, null,0);      // Yes, add IE style
         } else {                                         // Browser is IE?
            document.styleSheets[0].insertRule(ruleName+' { }', 0); // Yes, add Moz style.
         }                                                // End browser check
      }                                                   // End already exist check.
   }                                                      // End browser ability check.
   return getCSSRule(ruleName);                           // return rule we just created.
} 
@@ -687,17 +687,16 @@
 cssRule.
- 
 %0A       
@@ -1098,17 +1098,16 @@
 E style.
- 
 %0A       
@@ -1296,16 +1296,40 @@
 ctorText
+ && cssRule.selectorText
 .toLower
@@ -2825,17 +2825,16 @@
 tCSSRule
- 
 %0A%0Afuncti
@@ -2905,19 +2905,16 @@
 CSS rule
-   
 %0A   retu
@@ -4015,9 +4015,8 @@
 eated.%0A%7D
- 

add another null check in CSS logic to handle dark mode selector