Fix recent regression with cascading of params to content adapters

Fixes #13743

hugolib/cascade_test.go

@@ -917,3 +917,24 @@ title: p2
 	b.AssertFileExists("public/sx/index.html", true)    // failing
 	b.AssertFileExists("public/sx/p2/index.html", true) // failing
 }
+
+func TestCascadeGotmplIssue13743(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ['home','rss','section','sitemap','taxonomy','term']
+[cascade.params]
+foo = 'bar'
+[cascade.target]
+path = '/p1'
+-- content/_content.gotmpl --
+{{ .AddPage (dict "title" "p1" "path" "p1") }}
+-- layouts/all.html --
+{{ .Title }}|{{ .Params.foo }}
+`
+
+	b := Test(t, files)
+
+	b.AssertFileContent("public/p1/index.html", "p1|bar") // actual content is "p1|"
+}