fix bug where getunit converts a scalar argument to a 0d numpy array

[petercorke]

The problem in #144 is actually in getunit which returns a numpy array when passed a scalar. This is a more general problem that was picked up here.

The fix is simple. Tested by turning warnings on

% python -Wd
Python 3.10.16 (main, Dec 11 2024, 10:22:29) [Clang 14.0.6 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from spatialmath.base import angvec2r
>>> angvec2r(0.3, [1, 0, 0])
array([[ 1.        ,  0.        ,  0.        ],
       [ 0.        ,  0.95533649, -0.29552021],
       [ 0.        ,  0.29552021,  0.95533649]])
>>> 

[petercorke]

this needs more thought, this deprecation warning is everywhere in the code base...