`tt.optimize.tt_min.min_tens` does not work

[tzoiker]

tt.optimize.tt_min.min_tens does not work at least for ttpy==1.2.1

How to reproduce: example

import tt
from tt.optimize import tt_min
tens = tt.rand([3, 4, 5, 4, 3], 5, 3)
min_element = min(tens.full().flatten())
print("Minimize random 5-dimensional TT tensor with ranks equal to 3. " +
      "The minimal element is %f" % min_element)
val, point = tt_min.min_tens(tens, rmax=10, nswp=30)

Gives the following error:

Minimize random 5-dimensional TT tensor with ranks equal to 3. The minimal element is -15.459226
---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
/tmp/ipykernel_23243/3135023836.py in <module>
      5 print("Minimize random 5-dimensional TT tensor with ranks equal to 3. " +
      6       "The minimal element is %f" % min_element)
----> 7 val, point = tt_min.min_tens(tens, rmax=10, nswp=30)

~/storage/miniconda2/envs/cqfs/lib/python3.7/site-packages/tt/optimize/tt_min.py in min_tens(tens, rmax, nswp, verb, smooth_fun)
    214             lm = min_cur
    215             x_full = J[ind_cur, :]
--> 216             val = tens[x_full]
    217             if verb:
    218                 print('New record:', val, 'Point:', x_full, 'elements seen:', elements_seen)

~/storage/miniconda2/envs/cqfs/lib/python3.7/site-packages/tt/core/vector.py in __getitem__(self, index)
    173                 (self.r[i], self.n[i], self.r[i + 1]), order='F')
    174             cur_core = cur_core[
--> 175                 :, index[i], :].reshape(
    176                 (self.r[i], -1), order='F')
    177             if running_fact is None:

IndexError: only integers, slices (`:`), ellipsis (`...`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices