[lldb] Fix two bugs in ObjectContainerMachOFileset when reading from memory

[JDevlieghere]

Summary

Jason caught two issues in the memory part of ObjectContainerMachOFileset which I didn't hook up and therefore wasn't able to test.

[jasonmolenda]

Thanks! LGTM.

lldb/source/Plugins/ObjectContainer/Mach-O-Fileset/ObjectContainerMachOFileset.cpp

ObjectContainerMachOFileset::ObjectContainerMachOFileset(
     lldb::offset_t data_offset, const lldb_private::FileSpec *file,
     lldb::offset_t offset, lldb::offset_t length)
     : ObjectContainer(module_sp, file, offset, length, data_sp, data_offset),
       m_memory_addr(LLDB_INVALID_ADDRESS) {}
 
 ObjectContainerMachOFileset::ObjectContainerMachOFileset(
     const lldb::ModuleSP &module_sp, lldb::WritableDataBufferSP data_sp,
     const lldb::ProcessSP &process_sp, lldb::addr_t header_addr)
-    : ObjectContainer(module_sp, nullptr, 0, 0, data_sp, 0),
-      m_memory_addr(header_addr) {}
+    : ObjectContainer(module_sp, nullptr, 0, data_sp->GetByteSize(), data_sp,
+                      0),
+      m_process_wp(process_sp), m_memory_addr(header_addr) {}
 
 ObjectContainer *ObjectContainerMachOFileset::CreateInstance(
     const lldb::ModuleSP &module_sp, DataBufferSP &data_sp,
     lldb::offset_t data_offset, const FileSpec *file,
     lldb::offset_t file_offset, lldb::offset_t length) {
   if (!data_sp)
     return {};