fix: nil panic on old go.mod (issue #1100)

test/issue1100_test.go

@@ -0,0 +1,22 @@
+package test
+
+import (
+	"testing"
+
+	"github.com/mgechev/revive/lint"
+	"github.com/mgechev/revive/rule"
+)
+
+func TestIssue1100(t *testing.T) {
+	args := []any{map[string]any{
+		"maxLitCount": "2",
+		"allowStrs":   "\"\"",
+		"allowInts":   "0,1,2",
+		"allowFloats": "0.0,1.0",
+		"ignoreFuncs": "os\\.(CreateFile|WriteFile|Chmod|FindProcess),\\.Println,ignoredFunc,\\.Info",
+	}}
+
+	testRule(t, "goUnknown/issue1100", &rule.AddConstantRule{}, &lint.RuleConfig{
+		Arguments: args,
+	})
+}