NULL check in ConnectPro

Prevents service crash

Bug: 13744720
Change-Id: I7a5cdba830b4f96660f890ede6b94c38fc3108dd
diff --git a/services/camera/libcameraservice/CameraService.cpp b/services/camera/libcameraservice/CameraService.cpp
index 02bca1f..c6b4670 100644
--- a/services/camera/libcameraservice/CameraService.cpp
+++ b/services/camera/libcameraservice/CameraService.cpp
@@ -575,6 +575,11 @@
                                         /*out*/
                                         sp<IProCameraUser>& device)
 {
+    if (cameraCb == 0) {
+        ALOGE("%s: Callback must not be null", __FUNCTION__);
+        return BAD_VALUE;
+    }
+
     String8 clientName8(clientPackageName);
     int callingPid = getCallingPid();