DO NOT MERGE: libcameraservice: Fix nullptr crash when no client.

This change prevents a crash in the camera service when the camera
HAL notifies the service about the absence of a removable camera and
there happens to be no client connected to the service. It checks
that the pointer returned from clientToDisconnect.get() is non-null
before trying to dereference it (as is done in existing code
immediately below this change).

Bug: 25165323
Change-Id: I8055654bac980542e63ea7f52bf897eaafbc09bc
Signed-off-by: Tom Keel <thomas.keel@intel.com>
diff --git a/services/camera/libcameraservice/CameraService.cpp b/services/camera/libcameraservice/CameraService.cpp
index 2bb282f..3deb396 100644
--- a/services/camera/libcameraservice/CameraService.cpp
+++ b/services/camera/libcameraservice/CameraService.cpp
@@ -315,8 +315,10 @@
             clientToDisconnect = removeClientLocked(id);
 
             // Notify the client of disconnection
-            clientToDisconnect->notifyError(ICameraDeviceCallbacks::ERROR_CAMERA_DISCONNECTED,
-                    CaptureResultExtras{});
+            if (clientToDisconnect != nullptr) {
+                clientToDisconnect->notifyError(ICameraDeviceCallbacks::ERROR_CAMERA_DISCONNECTED,
+                        CaptureResultExtras{});
+            }
         }
 
         ALOGI("%s: Client for camera ID %s evicted due to device status change from HAL",