options: avoid OOR when called w/ no args

This would mean essentially a broken environment, but for fuzzer
coverage handling this case.

Bug: 195473218
Test: aidl_parser_fuzzer
Change-Id: If8101d232b614f2df072393be3f4ba1b017af2cf
diff --git a/options.cpp b/options.cpp
index d06276f..a4dafba 100644
--- a/options.cpp
+++ b/options.cpp
@@ -200,7 +200,7 @@
 }
 
 Options::Options(int argc, const char* const raw_argv[], Options::Language default_lang)
-    : myname_(raw_argv[0]), language_(default_lang) {
+    : myname_(argc >= 1 ? raw_argv[0] : "aidl"), language_(default_lang) {
   std::vector<const char*> argv = warning_options_.Parse(argc, raw_argv, error_message_);
   if (!Ok()) return;
   argc = argv.size();