Scaled `Lanczos` interpolator throws `MethodError` regarding the `lbound()` function

If I create a `ScaledInterpolation` with the `Lanczos` interpolator as follows
```julia
using Interpolations

x = 0:0.1:1.0
A = randn(length(x))
itp = scale(interpolate(A, Lanczos()), x)
```
and try to interpolate, e.g. `itp(0.33)`, a `MethodError` is thrown in the `checkbounds()` function. This error does not occur for the plain (unscaled) `Lanczos` interpolator.

It seems that an implementation of the function `lbound()` is missing for the scaled `Lanczos` interpolator.