fix: resolve state_unsafe_mutation in getChatVar() (#707)

# PR Checklist
- [ ] Have you checked if it works normally in all models? *Ignore this
if it doesn't use models.*
- [ ] Have you checked if it works normally in all web, local, and node
hosted versions? If it doesn't, have you blocked it in those versions?
- [ ] Have you added type definitions?

# Description
While investigating an issue where `{{getvar::A}}` didn't work properly
in background embedding, I encountered a `state_unsafe_mutation` error.
It appears that modifying the null check operator on the relevant line
can resolve this issue. Thank for your time.

src/ts/process/scripts.ts

@@ -277,6 +277,7 @@ export async function processScriptFull(char:character|groupChat|simpleCharacter
                 for(const m of meta){
                     if(m.startsWith('order ')){
                         order = parseInt(m.substring(6))
+                        orderChanged = true
                     }
                     else{
                         actions.push(m)