[WarnSystem] Bug fixes (version 1.3.13)

Squashed commit of the following:

commit e95b96b
Author: retke <laggron42@gmail.com>
Date:   Sun Feb 28 21:19:23 2021 +0100

    Fix UTC inconsistency

commit a96b4b3
Author: retke <laggron42@gmail.com>
Date:   Sun Feb 28 17:53:13 2021 +0100

    Handle empty time with automod warn show

    Resolves #146

warnsystem/api.py

@@ -1531,7 +1531,7 @@ def is_autowarn_valid(warn):
             # we increase this value until reaching the given limit
             time = autowarn["time"]
             if time:
-                until = datetime.now() - timedelta(seconds=time)
+                until = datetime.utcnow() - timedelta(seconds=time)
                 autowarns[i]["until"] = until
         del time
         found_warnings = {}  # we fill this list with the valid autowarns, there can be more than 1

warnsystem/automod.py

@@ -498,7 +498,7 @@ async def automod_warn_show(self, ctx: commands.Context, index: int):
             autowarn["warn"]["reason"],
             autowarn["level"],
             autowarn["automod_only"],
-            timedelta(seconds=autowarn["time"]),
+            timedelta(seconds=autowarn["time"]) if autowarn["time"] else None,
             timedelta(seconds=duration) if duration else None,
         )
         await ctx.send(embed=embed)