Warning information generated by spapi

When I use the spapi function as below, warning information is printed

>> spline = spapi([0, 0.1, 0.2, 0.3, 0.4, 1],[0, 0], [1, 1]) ;

Warning: Matrix is singular, close to singular or badly scaled. Results may be inaccurate. RCOND = NaN.

> In slvblk at 104

In spapi>spapi1 at 185

In spapi at 147

slvblk is the function that Solves almost block-diagonal linear system.

I just try to do simple experiment with the function spapi. The input is two points((0,0),(0,1) and hope to get the b spline with degree 3 between the two points, so the length of knot vector is 6. I don't understand why warning information is produced.