Fix a null object reference crash on Emoji Palette

Do nothing if the current EmojiPageKeyboardView is null.

BUG: 13006906
Change-Id: I169b70122ec939075b5be033953b48762fd528fc
diff --git a/java/src/com/android/inputmethod/keyboard/EmojiPalettesView.java b/java/src/com/android/inputmethod/keyboard/EmojiPalettesView.java
index 50e8163..c344643 100644
--- a/java/src/com/android/inputmethod/keyboard/EmojiPalettesView.java
+++ b/java/src/com/android/inputmethod/keyboard/EmojiPalettesView.java
@@ -724,7 +724,9 @@
             // canceled.
             final EmojiPageKeyboardView currentKeyboardView =
                     mActiveKeyboardViews.get(mActivePosition);
-            currentKeyboardView.releaseCurrentKey();
+            if (currentKeyboardView != null) {
+                currentKeyboardView.releaseCurrentKey();
+            }
         }
 
         @Override