Fix options parsing segfault

A command like this would segfault:

zeek -b test.zeek --debug

The issue was that `getopt_long` was using a null element to determine
what the end of the options array is. If it saw a non-null element after
`--debug` it would say it's the argument for optarg, even if it's beyond
`zeek_args.size()`. Instead, just make sure the array is
null-terminated.

src/Options.cc

@@ -424,11 +424,17 @@ Options parse_cmdline(int argc, char** argv) {
     opterr = 0;
 
     // getopt may permute the array, so need yet another array
-    auto zargs = std::make_unique<char*[]>(zeek_args.size());
+    //
+    // Make sure this array is one greater than zeek_args and ends in nullptr, otherwise
+    // getopt may go beyond the end of the array
+    auto zargs = std::make_unique<char*[]>(zeek_args.size() + 1);
 
     for ( size_t i = 0; i < zeek_args.size(); ++i )
         zargs[i] = zeek_args[i].data();
 
+    // Make sure getopt doesn't go past the end
+    zargs[zeek_args.size()] = nullptr;
+
     while ( (op = getopt_long(zeek_args.size(), zargs.get(), opts, long_opts, &long_optsind)) != EOF )
         switch ( op ) {
             case 'a': rval.parse_only = true; break;