Added early return to modals.init() if modal undefined to support…

… non-div `.open()`s ↞ [auto-sync from https://github.com/adamlui/ai-web-extensions/tree/main/chatgpt-auto-continue]

firefox/extension/components/modals.js

@@ -37,6 +37,7 @@ window.modals = {
     },
 
     init(modal) {
+        if (!modal) return // to support non-div this.open()s
         if (!this.styles) this.stylize() // to init/append stylesheet
         modal.classList.add('no-user-select', this.class) ; modal.parentNode.classList.add(`${this.class}-bg`)
         dom.fillStarryBG(modal) // add starry bg