Fix empty system role replacement (#1526)

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[^1]: Modifies the behavior of prompting, requesting, or handling
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[^2]: Over 80% of the code is AI generated.

## Summary

If `db.systemRoleReplacement` is blank, fallback to 'user'

## Related Issues

If `db.systemRoleReplacement` is blank, request sends role with empty
string.

## Changes

If `db.systemRoleReplacement` is blank, fallback to 'user'

Author: cubicj

src/ts/process/request/request.ts

@@ -368,7 +368,7 @@ export function reformater(formated:OpenAIChat[],modelInfo:LLMModel|LLMFlags[]){
         for(let i=0;i<formated.length;i++){
             if(formated[i].role === 'system'){
                 formated[i].content = db.systemContentReplacement ? db.systemContentReplacement.replace('{{slot}}', formated[i].content) : `system: ${formated[i].content}`
-                formated[i].role = db.systemRoleReplacement
+                formated[i].role = db.systemRoleReplacement || 'user'
             }
         }
     }