fix: initialize default OCIO config on first use

ColorManager::Init() (run by every Project construction) dereferenced
GetDefaultConfig() unconditionally. Any Project created before
SetUpDefaultConfig() crashed inside OCIO getCanonicalName on a null
config — the Windows CI SEGFAULT, where the suite order runs a
Project-creating test first. Reproduced locally by running
MainWindowLayoutInfo.AccessorsStoreAndRetrieve as the first suite.

app/node/color/colormanager/colormanager.cpp

@@ -68,6 +68,13 @@ QString ColorManager::GetConfigFilename() const
 
 OCIO::ConstConfigRcPtr ColorManager::GetDefaultConfig()
 {
+	// Set up on first use: Project construction calls ColorManager::Init()
+	// unconditionally, so without this any Project created before
+	// SetUpDefaultConfig() crashed dereferencing a null config.
+	if (!default_config_) {
+		SetUpDefaultConfig();
+	}
+
 	return default_config_;
 }