Fix visual shader expression parsing (#31853)

Fix visual shader expression parsing

scene/resources/visual_shader.cpp

@@ -2479,9 +2479,9 @@ String VisualShaderNodeExpression::generate_code(Shader::Mode p_mode, VisualShad
 
 	static Vector<String> post_symbols;
 	if (post_symbols.empty()) {
-		post_symbols.push_back("\0");
 		post_symbols.push_back("\t");
 		post_symbols.push_back("\n");
+		post_symbols.push_back(",");
 		post_symbols.push_back(";");
 		post_symbols.push_back("}");
 		post_symbols.push_back("]");