test: add test case for toToml error swallowing

Add a test case that verifies toToml returns "" on encoding errors
(e.g. map[int]string where keys are not strings), consistent with
how toYaml and toJson handle errors.

Signed-off-by: Gagan Gupta <realgagangupta@users.noreply.github.com>

pkg/engine/funcs_test.go

@@ -122,6 +122,12 @@ keyInElement1 = "valueInElement1"`,
 		tpl:    `{{ fromYamlArray . }}`,
 		expect: `[error unmarshaling JSON: while decoding JSON: json: cannot unmarshal object into Go value of type []interface {}]`,
 		vars:   `hello: world`,
+	}, {
+		// toToml should swallow errors and return "" like toYaml and toJson do.
+		// map[int]string cannot be encoded as TOML (keys must be strings).
+		tpl:    `{{ toToml . }}`,
+		expect: ``,
+		vars:   map[int]string{1: "one"},
 	}, {
 		// This should never result in a network lookup. Regression for #7955
 		tpl:    `{{ lookup "v1" "Namespace" "" "unlikelynamespace99999999" }}`,