descriptor_parse: crash with whitespace on pk() #72
Description
The following descriptor tr(03d1d1110030000000000120000000000000000000000000001370010912cd08cc,pk( L4rK1yDtCWekvXuE6oXD9jCYfFNV2cWRpVuPLBcCU2z8TrisoyY1)) fails to be parsed on rust-miniscript (key too short) and is successfully parsed on Bitcoin Core.
There is a whitespace on pk, instead of pk(KEY) is pk( KEY) which may cause this issue.