Composing any email fails if a signature is set on the sending account

[mpnordland]

Describe the bug
Composing any email fails if a signature is set on the sending account

Software Versions

• Python version: 3.8
• Alot version: 0.9

To Reproduce
Steps to reproduce the behaviour:

1. Open Alot
2. Press 'm' to compose
3. Press enter to confirm from address
4. See error

Error Log

DEBUG:ui:Got key (['m'], [109])
DEBUG:ui:cmdline: 'compose'
DEBUG:ui:search command string: "compose"
DEBUG:__init__:mode:search got commandline "compose"
DEBUG:__init__:ARGS: ['compose']
DEBUG:__init__:cmd parms {'sender': None, 'template': None, 'tags': None, 'subject': None, 'to': None, 'cc': None, 'bcc': None, 'attach': None, 'omit_signature': False, 'spawn': None, 'rest': []}
DEBUG:envelope:TEMPLATE: None
DEBUG:ui:Got key (['enter'], [10])
DEBUG:globals:has signature
DEBUG:globals:is file
ERROR:ui:Traceback (most recent call last):
  File "/usr/lib/python3.8/site-packages/alot/ui.py", line 716, in apply_command
    await cmd.apply(self)
  File "/usr/lib/python3.8/site-packages/alot/commands/globals.py", line 882, in apply
    await self.__apply(ui)
  File "/usr/lib/python3.8/site-packages/alot/commands/globals.py", line 1022, in __apply
    await self._set_signature(ui)
  File "/usr/lib/python3.8/site-packages/alot/commands/globals.py", line 872, in _set_signature
    self.envelope.body += '\n' + sigcontent
AttributeError: 'Envelope' object has no attribute 'body'

[pazz]

Thanks for reporting this! I've just pushed a fix to the master branch. Cheers