fix createCallback complaining on client side

shared/callback.lua

@@ -13,6 +13,7 @@
 --- end)
 --- ```
 function createCallback(callbackName, funct)
+    if isServer() then
         if isStarted(OXLibExport) then
             lib.callback.register(callbackName, funct)
         else
@@ -30,6 +31,7 @@ function createCallback(callbackName, funct)
                 print("^6Bridge^7: ^1ERROR^7: ^3Can't find any script to register callback with", callbackName)
             end
         end
+    end
 end
 
 --- Triggers a server callback and returns the result.