Auto merge of #13128 - emilio:stupidest-assertion-ever, r=SimonSapin

Fix debug assertion introduced in #13108 by me.

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---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #13125 (github issue number if applicable).

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- [x] These changes do not require tests because https://github.com/servo/servo/issues/13127

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I'm stupid, and when I did the last moving-the-code-around, I failed miserably
to double-check it in a debug build.

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components/style/restyle_hints.rs

@@ -470,10 +470,10 @@ impl DependencySet {
             return;
         }
         for dep in deps {
-            debug_assert!(state_changes.intersects(dep.sensitivities.states) ||
-                          attrs_changed && dep.sensitivities.attrs,
-                          "Testing a completely ineffective dependency?");
-            if !hint.intersects(dep.hint) {
+            debug_assert!((!state_changes.is_empty() && !dep.sensitivities.states.is_empty()) ||
+                          (attrs_changed && dep.sensitivities.attrs),
+                          "Testing a known ineffective dependency?");
+            if (attrs_changed || state_changes.intersects(dep.sensitivities.states)) && !hint.intersects(dep.hint) {
                 let matched_then =
                     matches_complex_selector(&dep.selector, snapshot, None,
                                              &mut StyleRelations::empty());