Fix CTS test: return value of PiP actions

PictureInPictureParams#getActions() started returning empty lists
instead of null when it became a public API.

Bug: 225181835
Fixes: 225181835
Test: atest PictureInPictureParamsBuilderTest#testBuildParams
Change-Id: Icf702a47437c33f74791dfca5437ccf27593b822
diff --git a/tests/tests/app/src/android/app/cts/PictureInPictureParamsBuilderTest.java b/tests/tests/app/src/android/app/cts/PictureInPictureParamsBuilderTest.java
index c9f1cf2..a99f176 100644
--- a/tests/tests/app/src/android/app/cts/PictureInPictureParamsBuilderTest.java
+++ b/tests/tests/app/src/android/app/cts/PictureInPictureParamsBuilderTest.java
@@ -60,7 +60,7 @@
         params = builder.build();
 
         assertTrue(Float.compare(0f, params.getAspectRatioFloat()) == 0);
-        assertNull(params.getActions());
+        assertTrue(params.getActions().isEmpty());
         assertNull(params.getSourceRectHint());
     }