Fixed plaintext-only embeds. closes #360

src/NadekoBot/Common/SmartText/SmartEmbedTextArray.cs

@@ -14,7 +14,10 @@ public sealed record SmartEmbedTextArray : SmartText
         if (Embeds is null)
             return Array.Empty<EmbedBuilder>();
 
-        return Embeds.Map(em => em.GetEmbed());
+        return Embeds
+            .Where(x => x.IsValid)
+            .Select(em => em.GetEmbed())
+            .ToArray();
     }
 
     public void NormalizeFields()