Fix various warnings

CMakeLists.txt

@@ -1,6 +1,8 @@
 # FindPython's Development.Module component was added in 3.18.
 # Require 3.18.2+ because pybind11 recommends it.
 cmake_minimum_required(VERSION 3.18.2)
+# This policy CMP0177 can be removed when we upgrade to CMake >= 3.31.
+cmake_policy(SET CMP0177 NEW)
 
 #------------------------------------------------------------------------------
 # Project Metadata

src/opentimelineio/serializableObject.h

@@ -162,7 +162,7 @@ class OTIO_API_TYPE SerializableObject
         template <typename T>
         bool read(std::string const& key, Retainer<T>* dest)
         {
-            SerializableObject* so;
+            SerializableObject* so = nullptr;
             if (!read(key, &so))
             {
                 return false;