Fix : don't print cube file if out_chg is 0

Author: dyzheng

source/src_io/write_rho_cube.cpp

@@ -9,7 +9,10 @@ void Charge::write_rho_cube(
 	const int &precision) 
 {
     ModuleBase::TITLE("Charge","write_rho_cube");
-
+	if (out_chg==0) 
+	{
+		return;
+	}
 	time_t start, end;
 	std::ofstream ofs;