With all plugins enabled Pluma shows "gi.repository.GLib.Error: gtk-source-completion-error-quark: Provider is not bound to this completion object (1)" in terminal on close

[Norbert]

Steps to reproduce:
1. Install Ubuntu MATE 19.04
2. Launch Pluma and enable all Plugins
3. Close Pluma
4. Launch terminal and issue `pluma` command
5. Close Pluma window

Expected results:
* Pluma closed without messages in the terminal

Actual results:
* Pluma closed with the following errors in the terminal:

Traceback (most recent call last):
  File "/usr/lib/x86_64-linux-gnu/pluma/plugins/snippets/Document.py", line 702, in on_view_destroy
    self.stop()
  File "/usr/lib/x86_64-linux-gnu/pluma/plugins/snippets/Document.py", line 70, in stop
    self.set_view(None)
  File "/usr/lib/x86_64-linux-gnu/pluma/plugins/snippets/Document.py", line 149, in set_view
    self._set_view(view)
  File "/usr/lib/x86_64-linux-gnu/pluma/plugins/snippets/Document.py", line 113, in _set_view
    completion.remove_provider(self.provider)
gi.repository.GLib.Error: gtk-source-completion-error-quark: Provider is not bound to this completion object (1)

Note: the 19.10 is also affected.

ProblemType: Bug
DistroRelease: Ubuntu 19.04
Package: pluma 1.20.4-1
ProcVersionSignature: Ubuntu 5.0.0-29.31-generic 5.0.21
Uname: Linux 5.0.0-29-generic x86_64
ApportVersion: 2.20.10-0ubuntu27.1
Architecture: amd64
CurrentDesktop: MATE
Date: Sat Oct 5 19:45:10 2019
InstallationDate: Installed on 2019-04-18 (169 days ago)
InstallationMedia: Ubuntu-MATE 19.04 "Disco Dingo" - Release amd64 (20190416)
SourcePackage: pluma
UpgradeStatus: No upgrade log present (probably fresh install)

[Norbert (nrbrtx)]

The 19.04 is EOL.
The 20.04 LTS is not affected.