servo: Merge #12241 - Don't load stylesheets in documents without bro…

…wsing contexts (from jdm:multiple-stylesheets); r=notriddle

Per whatwg/html#1495, this fixes the most commonly reported panic in nightlies by making us match what other browsers do.

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #12047 (github issue number if applicable).
- [X] There are tests for these changes OR

Source-Repo: https://github.com/servo/servo
Source-Revision: 61491447e21655a1eca01a85797b25a254525d98

UltraBlame original commit: 3d72d0ed4143696590799c52cc0f51697fc8f2f0

servo/components/script/dom/htmllinkelement.rs

@@ -1533,6 +1533,20 @@ document_from_node
 self
 )
 ;
+if
+document
+.
+browsing_context
+(
+)
+.
+is_none
+(
+)
+{
+return
+;
+}
 match
 document
 .