Added option to externally cancel progress bar

Personally, I think this feature should have been here a long time ago. I hope that adding this code will help players in the future and if anyone here has a suggestion for a code change feel free to comment.

[core]/esx_progressbar/Progress.lua

@@ -1,4 +1,5 @@
 local CurrentProgress = nil
+
 local function Progressbar(message,length,Options)
     if CurrentProgress then
         return false
@@ -34,9 +35,8 @@ local function Progressbar(message,length,Options)
     end
 end
 
-ESX.RegisterInput("cancelprog", "[ProgressBar] Cancel Progressbar", "keyboard", "BACK", function()
+local function CancelProgressbar()
     if not CurrentProgress then return end
-    if not CurrentProgress.onCancel then return end
     SendNUIMessage({
         type = "Close"
     })
@@ -44,7 +44,12 @@ ESX.RegisterInput("cancelprog", "[ProgressBar] Cancel Progressbar", "keyboard",
     if CurrentProgress.FreezePlayer then FreezeEntityPosition(PlayerPedId(), false) end
     CurrentProgress.canceled = true
     CurrentProgress.length = 0
-    CurrentProgress.onCancel()
     CurrentProgress = nil
+end
+
+ESX.RegisterInput("cancelprog", "[ProgressBar] Cancel Progressbar", "keyboard", "BACK", function()
+    CancelProgressbar()
 end)
+
 exports('Progressbar', Progressbar)
+exports('CancelProgressbar', CancelProgressbar)