public GenericRequestBuilder<ModelType, DataType, ResourceType, TranscodeType> fallback(
            int resourceId) {
        this.fallbackResource = resourceId;

        return this;
    }
Sets a resource to display if the model provided to {@link #load(Object)} is {@code null}.

<p>
  If a fallback is not set, null models will cause the error drawable to be displayed. If
  the error drawable is not set, the placeholder will be displayed.
</p>

@see #placeholder(Drawable)
@see #placeholder(int)

@param resourceId The id of the resource to use as a fallback.
@return This request builder.
core/src/main/java/com/bumptech/glide/GenericRequestBuilder.java