Show a meaningful message if users try to login without a paid account.

app/assets/js/authmanager.js

@@ -29,12 +29,17 @@ const loggerSuccess = LoggerUtil('%c[AuthManager]', 'color: #209b07; font-weight
 exports.addAccount = async function(username, password){
     try {
         const session = await Mojang.authenticate(username, password, ConfigManager.getClientToken())
+        if(session.selectedProfile != null){
             const ret = ConfigManager.addAuthAccount(session.selectedProfile.id, session.accessToken, username, session.selectedProfile.name)
             if(ConfigManager.getClientToken() == null){
                 ConfigManager.setClientToken(session.clientToken)
             }
             ConfigManager.save()
             return ret
+        } else {
+            throw new Error('NotPaidAccount')
+        }
+        
     } catch (err){
         return Promise.reject(err)
     }

app/assets/js/scripts/login.js

@@ -206,11 +206,18 @@ function resolveError(err){
         }
     }
     if(err.message != null){
+        if(err.message === 'NotPaidAccount'){
+            return {
+                title: 'Error During Login:<br>Game Not Purchased',
+                desc: 'The account you are trying to login with has not purchased a copy of Minecraft.<br>You may purchase a copy on <a href="https://minecraft.net/">Minecraft.net</a>'
+            }
+        } else {
             // Unknown error with request.
             return {
                 title: 'Error During Login:<br>Unknown Error',
                 desc: err.message
             }
+        }
     } else {
         // Unknown Mojang error.
         return {
@@ -234,11 +241,11 @@ function loginCancelEnabled(val){
 
 loginCancelButton.onclick = (e) => {
     switchView(getCurrentView(), loginViewOnCancel, 500, 500, () => {
+        loginUsername.value = ''
+        loginPassword.value = ''
         loginCancelEnabled(false)
         if(loginViewCancelHandler != null){
             loginViewCancelHandler()
-            loginUsername.value = ''
-            loginPassword.value = ''
             loginViewCancelHandler = null
         }
     })