fix: identity-check incognito-listener clear to survive overlapping IME teardown

KeyboardManager is a process singleton; FlorisImeService.onDestroy cleared its
incognitoModeChangedListener unconditionally. During an overlapping service
teardown/recreate (config change, theme switch, OOM rebind) the framework can run
the new service's onCreate (which registers a fresh listener) before the old
service's onDestroy, so the old clear() would null the live listener — leaving
FLAG_SECURE un-reapplied on a runtime incognito toggle until the next input start.
clearIncognitoModeChangedListener now only nulls the field when it still holds the
caller's own listener reference.

Author: SysAdminDoc

app/src/main/kotlin/dev/patrickgold/florisboard/FlorisImeService.kt

@@ -546,7 +546,7 @@ class FlorisImeService : LifecycleInputMethodService() {
         try { NlpInlineAutofill.clearInlineSuggestions() } catch (e: Exception) {
             flogWarning(LogTopic.IMS_EVENTS) { "NlpInlineAutofill.clearInlineSuggestions() failed: $e" }
         }
-        keyboardManager.clearIncognitoModeChangedListener()
+        keyboardManager.clearIncognitoModeChangedListener(flagSecureIncognitoModeChangedListener)
         FlorisImeServiceReference = WeakReference(null)
         super.onDestroy()
     }

app/src/main/kotlin/dev/patrickgold/florisboard/ime/keyboard/KeyboardManager.kt

@@ -253,8 +253,16 @@ class KeyboardManager(context: Context) : InputKeyEventReceiver {
         incognitoModeChangedListener = listener
     }
 
-    fun clearIncognitoModeChangedListener() {
-        incognitoModeChangedListener = null
+    fun clearIncognitoModeChangedListener(listener: ((Boolean) -> Unit)? = null) {
+        // Identity-checked clear: KeyboardManager is a process singleton, so a
+        // torn-down IME service must not wipe a listener that a newer service
+        // instance already registered during an overlapping teardown/recreate
+        // (config change, theme switch, OOM rebind). A null argument keeps the
+        // legacy unconditional behaviour for any caller that does not track its
+        // own listener reference.
+        if (listener == null || incognitoModeChangedListener === listener) {
+            incognitoModeChangedListener = null
+        }
     }
 
     fun reevaluateInputShiftState() {