Add default values for the channel fields without existing defaults.

app/src/main/java/com/github/libretube/api/obj/Channel.kt

@@ -4,11 +4,11 @@ import kotlinx.serialization.Serializable
 
 @Serializable
 data class Channel(
-    val id: String,
-    val name: String,
-    val avatarUrl: String,
+    val id: String? = null,
+    val name: String? = null,
+    val avatarUrl: String? = null,
     val bannerUrl: String? = null,
-    val description: String,
+    val description: String = "",
     val nextpage: String? = null,
     val subscriberCount: Long = 0,
     val verified: Boolean = false,

app/src/main/java/com/github/libretube/ui/fragments/ChannelFragment.kt

@@ -142,7 +142,7 @@ class ChannelFragment : BaseFragment() {
 
                 binding.channelShare.setOnClickListener {
                     val shareDialog = ShareDialog(
-                        response.id.toID(),
+                        response.id!!.toID(),
                         ShareObjectType.CHANNEL,
                         shareData
                     )