Camera2: Add null check to createStream

Prevent a native null dereference crash.

bug: 15332257
Change-Id: I10c4053a0b4f07fbf52c37dd2f2853b501def669
diff --git a/services/camera/libcameraservice/api2/CameraDeviceClient.cpp b/services/camera/libcameraservice/api2/CameraDeviceClient.cpp
index 4fce1b3..8154e59 100644
--- a/services/camera/libcameraservice/api2/CameraDeviceClient.cpp
+++ b/services/camera/libcameraservice/api2/CameraDeviceClient.cpp
@@ -310,6 +310,10 @@
 
     Mutex::Autolock icl(mBinderSerializationLock);
 
+    if (bufferProducer == NULL) {
+        ALOGE("%s: bufferProducer must not be null", __FUNCTION__);
+        return BAD_VALUE;
+    }
     if (!mDevice.get()) return DEAD_OBJECT;
 
     // Don't create multiple streams for the same target surface