[regexp] Throw on invalid capture group names in replacer string

src/runtime/runtime-strings.cc

Index: src/runtime/runtime-strings.cc
diff --git a/src/runtime/runtime-strings.cc b/src/runtime/runtime-strings.cc
index 6f21051891f665f34d05b67ea625fca299106a8c..1ef04ed467f66112cc7dd4dcdb978ba9716896be 100644
--- a/src/runtime/runtime-strings.cc
+++ b/src/runtime/runtime-strings.cc
@@ -41,8 +41,9 @@ RUNTIME_FUNCTION(Runtime_GetSubstitution) {
       return match_;  // Return arbitrary string handle.
     }
     MaybeHandle<String> GetNamedCapture(Handle<String> name,
-                                        bool* capture_exists) override {
+                                        CaptureState* state) override {
       UNREACHABLE();
+      *state = INVALID;
       return MaybeHandle<String>();
     }