Improve check for invalid connection request

The check currently relies on the default value of 0 returned if the
Bundle doesn't define a pid. But in some cases, like Robolectric unit tests,
0 is a possible pid. The check can be improved by directly asserting that
the value is defined.

PiperOrigin-RevId: 521414649
(cherry picked from commit 694d690)

Author: tonihei

libraries/session/src/main/java/androidx/media3/session/ConnectionRequest.java

@@ -89,8 +89,8 @@ public Bundle toBundle() {
         int controllerInterfaceVersion =
             bundle.getInt(FIELD_CONTROLLER_INTERFACE_VERSION, /* defaultValue= */ 0);
         String packageName = checkNotNull(bundle.getString(FIELD_PACKAGE_NAME));
-        int pid = bundle.getInt(FIELD_PID, /* defaultValue= */ 0);
-        checkArgument(pid != 0);
+        checkArgument(bundle.containsKey(FIELD_PID));
+        int pid = bundle.getInt(FIELD_PID);
         @Nullable Bundle connectionHints = bundle.getBundle(FIELD_CONNECTION_HINTS);
         return new ConnectionRequest(
             libraryVersion,