Fix compilation error in ObjectFileMachO::ParseSymtab

Author: vedantk

lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp

@@ -2737,9 +2737,12 @@ size_t ObjectFileMachO::ParseSymtab() {
                      nlist_index++) {
                   /////////////////////////////
                   {
-                    struct nlist_64 nlist;
-                    if (!ParseNList(dsc_local_symbols_data, nlist_data_offset, nlist_byte_size, nlist)
+                    llvm::Optional<struct nlist_64> nlist_maybe =
+                        ParseNList(dsc_local_symbols_data, nlist_data_offset,
+                                   nlist_byte_size);
+                    if (!nlist_maybe)
                       break;
+                    struct nlist_64 nlist = *nlist_maybe;
 
                     SymbolType type = eSymbolTypeInvalid;
                     const char *symbol_name = dsc_local_symbols_data.PeekCStr(