[FIX] compiler: compile named slot in t-component in named slot

Previously, if a t-set-slot was inside a t-component itself inside a
t-set-slot the parser would crash, because the slot is removed from the
template before compiling its content, causing a further check's
assumption to be broken (the t-set-slot remains connected to the
component's xml node)

src/compiler/parser.ts

@@ -740,14 +740,14 @@ function parseComponent(node: Element, ctx: ParsingContext): AST | null {
       // be ignored)
       let el = slotNode.parentElement!;
       let isInSubComponent = false;
-      while (el !== clone) {
+      while (el && el !== clone) {
         if (el!.hasAttribute("t-component") || el!.tagName[0] === el!.tagName[0].toUpperCase()) {
           isInSubComponent = true;
           break;
         }
         el = el.parentElement!;
       }
-      if (isInSubComponent) {
+      if (isInSubComponent || !el) {
         continue;
       }