Tolerate nil target in param.Expand

Signed-off-by: Ilya <rihter007@inbox.ru>

Author: rihter007

pkg/test/parameter.go

@@ -62,7 +62,7 @@ func (p *Param) Expand(target *target.Target, vars StepsVariablesReader) (string
 		return "", errors.New("parameter cannot be nil")
 	}
 	funcs := getFuncMap()
-	if vars != nil {
+	if target != nil && vars != nil {
 		registerStepVariableAccessor(funcs, target.ID, vars)
 	}
 	// use Go text/template from here

pkg/test/parameter_test.go

@@ -56,6 +56,18 @@ func TestParameterExpandUserFunctions(t *testing.T) {
 	require.Error(t, UnregisterFunction("NoSuchFunction"))
 }
 
+func TestExpandWithNoTargetProvided(t *testing.T) {
+	p := NewParam("dummy")
+
+	res, err := p.Expand(nil, nil)
+	require.NoError(t, err)
+	require.Equal(t, "dummy", res)
+
+	res, err = p.Expand(nil, newStepsVariablesMock())
+	require.NoError(t, err)
+	require.Equal(t, "dummy", res)
+}
+
 func TestStepVariablesExpand(t *testing.T) {
 	p := NewParam("{{ StringVar \"step1.string_var\" }}: {{ IntVar \"step1.int_var\" }}")
 	svm := newStepsVariablesMock()