Fix occasional 'unknown error' in override command

BirthdayBot/BirthdayBot.vbproj

@@ -4,7 +4,7 @@
     <OutputType>Exe</OutputType>
     <RootNamespace>BirthdayBot</RootNamespace>
     <TargetFramework>netcoreapp2.0</TargetFramework>
-    <Version>1.4.0</Version>
+    <Version>1.4.1</Version>
     <Authors>Noi</Authors>
     <Company />
     <Description>Discord bot for birthday reminders.</Description>

BirthdayBot/UserInterface/ManagerCommands.vb

@@ -319,6 +319,10 @@ Friend Class ManagerCommands
             Return
         End If
         Dim overuser = reqChannel.Guild.GetUser(user)
+        If overuser Is Nothing Then
+            Await reqChannel.SendMessageAsync(BadUserError)
+            Return
+        End If
 
         ' Third parameter: determine command to invoke.
         ' Reminder that we're only receiving a param array of size 3 at maximum. String must be split again.