camera2: Don't NPE when closing the CameraDevice

Bug: 10360518
Change-Id: I0154e12490a063adea753c0aa6ae422605ba5ac5
diff --git a/core/java/android/hardware/camera2/impl/CameraDevice.java b/core/java/android/hardware/camera2/impl/CameraDevice.java
index 64e4dc9..86a073f 100644
--- a/core/java/android/hardware/camera2/impl/CameraDevice.java
+++ b/core/java/android/hardware/camera2/impl/CameraDevice.java
@@ -301,7 +301,9 @@
         synchronized (mLock) {
 
             try {
-                mRemoteDevice.disconnect();
+                if (mRemoteDevice != null) {
+                    mRemoteDevice.disconnect();
+                }
             } catch (CameraRuntimeException e) {
                 throw e.asChecked();
             } catch (RemoteException e) {