Camera: Avoid possible NPE after extension session configuration

Camera extension clients are able to close and release camera and
all associated extension resources while an advanced extension session
configuration is in progress.
In case, the extension initializer callback gets executed after all
resources are released it may try to access the already released
binder interface triggering NPE.

Bug: 268437036
Test: atest -c -d
cts/tests/camera/src/android/hardware/camera2/cts/CameraExtensionSessionTest.java

Change-Id: Ib6fdc9d08e973616dc7d83264dc3f320e496cbd3

core/java/android/hardware/camera2/impl/CameraAdvancedExtensionSessionImpl.java

@@ -528,8 +528,15 @@ public final class CameraAdvancedExtensionSessionImpl extends CameraExtensionSes
             boolean status = true;
             synchronized (mInterfaceLock) {
                 try {
-                    mSessionProcessor.onCaptureSessionStart(mRequestProcessor);
-                    mInitialized = true;
+                    if (mSessionProcessor != null) {
+                        mSessionProcessor.onCaptureSessionStart(mRequestProcessor);
+                        mInitialized = true;
+                    } else {
+                        Log.v(TAG, "Failed to start capture session, session released before " +
+                                "extension start!");
+                        status = false;
+                        mCaptureSession.close();
+                    }
                 } catch (RemoteException e) {
                     Log.e(TAG, "Failed to start capture session,"
                             + " extension service does not respond!");