Add check for empty text in sayTTS function

Signed-off-by: hashcoko <hashcoko@gmail.com>

src/ts/process/tts.ts

@@ -149,6 +149,9 @@ export async function sayTTS(character:character,text:string) {
         }
         case 'novelai': {
             const audioContext = new AudioContext();
+            if(text === ''){
+                alertError(language.errors.emptyText)
+            }
             const response = await globalFetch(`https://api.novelai.net/ai/generate-voice?text=${text}&voice=-1&seed=${character.naittsConfig.voice}&opus=false&version=${character.naittsConfig.version}`, {
                 method: 'GET',
                 headers: {