[refactor] Limit the condition of the option tag to "selected" attribute in isFormAttribute()

The condition of the option tag is intended to fix #1916 and should be evaluated in conjunction with the "selected" attribute.
This commit will improve code readability a bit, reduce the number of times to evaluate tags and also reduce the number of times to set the same attribute in option elements redundantly.

Author: kfule

render/render.js

@@ -730,7 +730,7 @@ module.exports = function() {
 		}
 	}
 	function isFormAttribute(vnode, attr) {
-		return attr === "value" || attr === "checked" || attr === "selectedIndex" || attr === "selected" && vnode.dom === activeElement(vnode.dom) || vnode.tag === "option" && vnode.dom.parentNode === activeElement(vnode.dom)
+		return attr === "value" || attr === "checked" || attr === "selectedIndex" || attr === "selected" && (vnode.dom === activeElement(vnode.dom) || vnode.tag === "option" && vnode.dom.parentNode === activeElement(vnode.dom))
 	}
 	function isLifecycleMethod(attr) {
 		return attr === "oninit" || attr === "oncreate" || attr === "onupdate" || attr === "onremove" || attr === "onbeforeremove" || attr === "onbeforeupdate"