`pmcx.mcxlab` fails to typecast `traj.id` output from float32 to uint32

[fangq]

please see the bug report by Gijs Buist in this mailing list post:

https://groups.google.com/g/mcx-users/c/O79Yk4G8_xM

the example to reproduce the issue

###### code ########

#%% []
import numpy as np
import pmcx
import matplotlib.pyplot as plt
from struct import unpack

#%%[]

print(pmcx.__version__)

cfg={}
cfg['nphoton']=1e1
cfg['vol']=np.ones([60, 60, 60], dtype='uint8')
cfg['vol'][20:40, 30:40, 20:30]=2
cfg['tstart']=0
cfg['tend']=5e-9
cfg['tstep']=5e-9
cfg['srcpos']=[30,30,0]
cfg['srcdir']=[0,0,1]
cfg['prop']=[[0, 0, 1, 1], [0.005, 1, 0.01, 1.37], [0.1, 10, 0.9, 1]]
cfg['detpos']=[[30,20,0,1]]        # to detect photons, one must first define detectors
cfg['debuglevel'] = 'M'

res = pmcx.mcxlab(cfg)

print(res.keys())
print(res['traj'].keys())
print(np.all(res['traj']['id'] == 0))

### output is c struct that needs to be converted to integers in the photon id case (other cases are floats which numpy automatically assumes I guess)
structAr = np.asarray(res['traj']['data'][0], order = 'C')
lenstr = str(len(structAr))
traj_id =  np.array( unpack( lenstr + 'I', structAr))
print(np.all(traj_id == 0))

plt.figure()
plt.plot(res['traj']['id'])
plt.show()


res2 = pmcx.run(cfg)

print(res.keys())
print(res2['traj'].shape)


### output is c struct that needs to be converted to integers in the photon id case (other cases are floats which numpy automatically assumes I guess)
structAr = np.asarray(res2['traj'][0], order = 'C')
lenstr = str(len(structAr))
traj_id =  np.array( unpack( lenstr + 'I', structAr))
print(np.all(traj_id == 0))

plt.figure()
plt.plot(traj_id)
plt.show()