Restore a mistakenly-removed null check

Passing null to camera.setPreviewDisplay() needs to work; this
restores the behavior from before the Surface/SurfaceControl
refactoring.

Bug: 8225538
Change-Id: Ib73bfa9fe53457a41a69b7fe5dfff3a3aa260f52
diff --git a/core/jni/android_hardware_Camera.cpp b/core/jni/android_hardware_Camera.cpp
index 7c65662..c0e12da 100644
--- a/core/jni/android_hardware_Camera.cpp
+++ b/core/jni/android_hardware_Camera.cpp
@@ -537,7 +537,10 @@
     sp<Camera> camera = get_native_camera(env, thiz, NULL);
     if (camera == 0) return;
 
-    sp<Surface> surface = android_view_Surface_getSurface(env, jSurface);
+    sp<Surface> surface;
+    if (jSurface) {
+        surface = android_view_Surface_getSurface(env, jSurface);
+    }
 
     if (camera->setPreviewDisplay(surface) != NO_ERROR) {
         jniThrowException(env, "java/io/IOException", "setPreviewDisplay failed");