make Status.filtered nullable to make some weird api implementations work again (#4426)

closes https://github.com/tuskyapp/Tusky/issues/4424

app/src/main/java/com/keylesspalace/tusky/entity/Status.kt

@@ -56,8 +56,9 @@ data class Status(
     val card: Card? = null,
     /** ISO 639 language code for this status. */
     val language: String? = null,
-    /** If the current token has an authorized user: The filter and keywords that matched this status. */
-    val filtered: List<FilterResult> = emptyList()
+    /** If the current token has an authorized user: The filter and keywords that matched this status.
+     *  Iceshrimp and maybe other implementations explicitly send filtered=null so we can't default to empty list. */
+    val filtered: List<FilterResult>? = null
 ) {
 
     val actionableId: String

app/src/main/java/com/keylesspalace/tusky/network/FilterModel.kt

@@ -47,7 +47,7 @@ class FilterModel @Inject constructor() {
             }
         }
 
-        val matchingKind = status.filtered.filter { result ->
+        val matchingKind = status.filtered.orEmpty().filter { result ->
             result.filter.kinds.contains(kind)
         }