Fix crash when opening settings after upgrading from previous version and having old theme selected

Simplenote/src/main/java/com/automattic/simplenote/PreferencesFragment.java

@@ -215,9 +215,6 @@ public boolean onPreferenceChange(Preference preference, Object newValue) {
             }
 
             private void updateTheme(Activity activity, int index) {
-                CharSequence[] entries = themePreference.getEntries();
-                themePreference.setSummary(entries[index]);
-
                 AnalyticsTracker.track(
                         AnalyticsTracker.Stat.SETTINGS_THEME_UPDATED,
                         AnalyticsTracker.CATEGORY_USER,

Simplenote/src/main/java/com/automattic/simplenote/utils/SafeThemeListPreference.kt

@@ -0,0 +1,42 @@
+package com.automattic.simplenote.utils
+
+import android.content.Context
+import android.util.AttributeSet
+import androidx.preference.ListPreference
+
+/**
+ * Custom ListPreference that handles invalid index values to prevent ArrayIndexOutOfBoundsException.
+ * This preference safely handles cases where the stored value doesn't match any of the available entries.
+ */
+class SafeThemeListPreference @JvmOverloads constructor(
+    context: Context,
+    attrs: AttributeSet? = null,
+    defStyleAttr: Int = androidx.preference.R.attr.preferenceStyle,
+    defStyleRes: Int = 0
+) : ListPreference(context, attrs, defStyleAttr, defStyleRes) {
+
+    override fun getSummary(): CharSequence? {
+        val value = getValue()
+        val entries = getEntries()
+
+        if (entries == null || entries.isEmpty()) {
+            return super.getSummary()
+        }
+
+        val index = findIndexOfValue(value)
+
+        // If index is invalid (out of bounds or -1), fallback to default value
+        return if (index >= 0 && index < entries.size) {
+            entries[index]
+        } else {
+            // Get the default value (2 = theme_system) and return its entry
+            val defaultIndex = findIndexOfValue("2")
+            if (defaultIndex >= 0 && defaultIndex < entries.size) {
+                entries[defaultIndex]
+            } else {
+                // Ultimate fallback - return the first entry
+                entries[0]
+            }
+        }
+    }
+}

Simplenote/src/main/res/xml/preferences.xml

@@ -41,15 +41,14 @@
         android:key="pref_key_appearance_preferences"
         android:title="@string/appearance">
 
-        <ListPreference
+        <com.automattic.simplenote.utils.SafeThemeListPreference
             android:key="pref_key_theme"
             android:defaultValue="2"
             android:entries="@array/array_theme_names"
             android:entryValues="@array/array_theme_values"
-            android:summary="%s"
             android:title="@string/theme"
             tools:summary="@string/theme_system">
-        </ListPreference>
+        </com.automattic.simplenote.utils.SafeThemeListPreference>
 
         <Preference
             android:key="pref_key_style"