fix crash with no camera avail

camerakit/src/main/java/com/flurgle/camerakit/PreviewImpl.java

@@ -67,6 +67,7 @@ public abstract class PreviewImpl {
         this.mTrueWidth = width;
         this.mTrueHeight = height;
 
+        if (width != 0 && height != 0) {
             AspectRatio aspectRatio = AspectRatio.of(width, height);
             int targetHeight = (int) (getView().getWidth() * aspectRatio.toFloat());
             float scaleY;
@@ -82,6 +83,7 @@ public abstract class PreviewImpl {
                 getView().setScaleX(1 / scaleY);
             }
         }
+    }
 
     int getTrueWidth() {
         return mTrueWidth;