App::get_options(): Assert correct usage

This is intended to catch cases where a developer erroneously includes the leading dash character in the name of a command-line option when invoking the App::get_options() or App::get_option_value() function.

core/app.cpp

@@ -1199,6 +1199,8 @@ void init(int cmdline_argc, const char *const *cmdline_argv) {
 }
 
 const std::vector<ParsedOption> get_options(const std::string &name) {
+  assert(!name.empty());
+  assert(name[0] != '-');
   std::vector<ParsedOption> matches;
   for (size_t i = 0; i < option.size(); ++i) {
     assert(option[i].opt);