Fix dismissing gesture floating preview

Bug: 8063926
Change-Id: I3b5b29ea0d5e4833e10e830dbdb086c868cd4884
diff --git a/java/src/com/android/inputmethod/keyboard/internal/GestureFloatingPreviewText.java b/java/src/com/android/inputmethod/keyboard/internal/GestureFloatingPreviewText.java
index 0954a7a..28655a9 100644
--- a/java/src/com/android/inputmethod/keyboard/internal/GestureFloatingPreviewText.java
+++ b/java/src/com/android/inputmethod/keyboard/internal/GestureFloatingPreviewText.java
@@ -157,6 +157,7 @@
      */
     protected void updatePreviewPosition() {
         if (mSuggestedWords.isEmpty() || TextUtils.isEmpty(mSuggestedWords.getWord(0))) {
+            getDrawingView().invalidate();
             return;
         }
         final String text = mSuggestedWords.getWord(0);