Prevent out of bounds error when post has no title

postrender.go

@@ -182,6 +182,10 @@ func applyMarkdownSpecial(data []byte, skipNoFollow bool, baseURL string, cfg *c
 }
 
 func applyBasicMarkdown(data []byte) string {
+	if len(data) == 0 {
+		return ""
+	}
+
 	mdExtensions := 0 |
 		blackfriday.EXTENSION_STRIKETHROUGH |
 		blackfriday.EXTENSION_SPACE_HEADERS |

postrender_test.go

@@ -18,6 +18,7 @@ func TestApplyBasicMarkdown(t *testing.T) {
 		in     string
 		result string
 	}{
+		{"empty", "", ""},
 		{"plain", "Hello, World!", "Hello, World!"},
 		{"multibyte", "こんにちは", `こんにちは`},
 		{"bold", "**안녕하세요**", `<strong>안녕하세요</strong>`},