Proxmox inventory plugin - Fix tags parsing (#4378) (#4402)

* Proxmox inventory plugin - Fix tags parsing

  * In some cases the Proxmox API returns a tags string that consists in
    a single space. The Proxmox inventory plugin parsed that into a
    single, empty tag. Stripping the initial string then checking
    whether it actually contains something fixes that.
  * Do not call `_to_safe` on the concatenation of a known safe string
    and a string that was already made safe.

* Changelog fragment for Proxmox inventory plugin tags fix

* Proxmox inventory plugin - Include link to PR in fragment

Co-authored-by: Felix Fontein <felix@fontein.de>

Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit 622895fb55)

Co-authored-by: Emmanuel Benoît <tseeker@nocternity.net>

changelogs/fragments/4378-proxmox-inventory-tags.yml

@@ -0,0 +1,4 @@
+---
+bugfixes:
+  - proxmox inventory plugin - fixed the ``tags_parsed`` field when Proxmox
+    returns a single space for the ``tags`` entry (https://github.com/ansible-collections/community.general/pull/4378).

plugins/inventory/proxmox.py

@@ -323,8 +323,10 @@ class InventoryModule(BaseInventoryPlugin, Constructable, Cacheable):
 
                 # Additional field containing parsed tags as list
                 if config == 'tags':
-                    parsed_key = self.to_safe('%s%s' % (key, "_parsed"))
-                    properties[parsed_key] = [tag.strip() for tag in value.split(",")]
+                    stripped_value = value.strip()
+                    if stripped_value:
+                        parsed_key = key + "_parsed"
+                        properties[parsed_key] = [tag.strip() for tag in stripped_value.split(",")]
 
                 # The first field in the agent string tells you whether the agent is enabled
                 # the rest of the comma separated string is extra config for the agent