fix: resizing sentence initialises as undefined

modules/generative_grammar/grammar.cpp

@@ -89,6 +89,9 @@ void Sentence::set_size(Vector2i value) {
 	this->size = value;
 	this->symbols.clear();
 	this->symbols.resize_initialized(this->size.x * this->size.y);
+	for (int i{ 0 }; i < this->symbols.size(); ++i) {
+		this->symbols.set(i, U'u');
+	}
 }
 
 Vector2i Sentence::get_size() const {