fix: continue registration if user submits valid number for age

src/main/kotlin/me/theentropyshard/kvinchik/Routing.kt

@@ -16,7 +16,7 @@ fun Router<*>.routing() {
             handle {
                 val keyboard = inlineKeyboard {
                     row {
-                        button(update.message!!.from!!.firstName, "username")
+                        button(message.from!!.firstName, "username")
                     }
                 }
 
@@ -52,9 +52,16 @@ fun Router<*>.routing() {
         text {
             handle {
                 val age = message.text!!
+
+                try {
+                    age.toInt()
+
                     data.set("age", age)
                     setState(StartStates.WaitingCity)
                     message.answer("Well, in which city do you live?")
+                } catch (e: NumberFormatException) {
+                    message.answer("Wrong input! Age must be a valid number!")
+                }
             }
         }
     }