fix crash on old mastodon instances

app/src/main/java/com/keylesspalace/tusky/AccountActivity.kt

@@ -325,8 +325,8 @@ class AccountActivity : BottomSheetActivity(), ActionButtonActivity, HasSupportF
                     .load(account.header)
                     .into(accountHeaderImageView)
 
-            accountFieldAdapter.fields = account.fields
+            accountFieldAdapter.fields = account.fields ?: emptyList()
-            accountFieldAdapter.emojis = account.emojis
+            accountFieldAdapter.emojis = account.emojis ?: emptyList()
             accountFieldAdapter.notifyDataSetChanged()
 
             if (account.moved != null) {

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

@@ -41,8 +41,8 @@ data class Account(
         @SerializedName("statuses_count") val statusesCount: Int,
         val source: AccountSource?,
         val bot: Boolean,
-        val emojis: List<Emoji> = emptyList(),
+        val emojis: List<Emoji>?,  // nullable for backward compatibility
-        val fields: List<Field> = emptyList(),
+        val fields: List<Field>?,  //nullable for backward compatibility
         val moved: Account? = null
 
 ) : Parcelable {

app/src/main/java/com/keylesspalace/tusky/util/CustomEmojiHelper.java

@@ -42,13 +42,13 @@ public class CustomEmojiHelper {
     /**
      * replaces emoji shortcodes in a text with EmojiSpans
      * @param text the text containing custom emojis
-     * @param emojis a list of the custom emojis
+     * @param emojis a list of the custom emojis (nullable for backward compatibility with old mastodon instances)
      * @param textView a reference to the textView the emojis will be shown in
      * @return the text with the shortcodes replaced by EmojiSpans
      */
-    public static Spanned emojifyText(@NonNull Spanned text, @NonNull List<Emoji> emojis, @NonNull final TextView textView) {
+    public static Spanned emojifyText(@NonNull Spanned text, @Nullable List<Emoji> emojis, @NonNull final TextView textView) {
 
-        if (!emojis.isEmpty()) {
+        if (emojis != null && !emojis.isEmpty()) {
 
             SpannableStringBuilder builder = new SpannableStringBuilder(text);
             for (Emoji emoji : emojis) {
@@ -71,7 +71,7 @@ public class CustomEmojiHelper {
         return text;
     }
 
-    public static Spanned emojifyString(@NonNull String string, @NonNull List<Emoji> emojis, @NonNull final TextView textView) {
+    public static Spanned emojifyString(@NonNull String string, @Nullable List<Emoji> emojis, @NonNull final TextView textView) {
         return emojifyText(new SpannedString(string), emojis, textView);
     }