repair gltf_viewer drag&drop

Drag and dropping a gltf folder was broken:
- the handle didn't find the gltf file on drag&drop
- the ResourceLoader cached the asset path
- don't exit(1) when drag&dropping an invalid file

libs/gltfio/src/ResourceLoader.cpp

@@ -74,15 +74,15 @@ enum class CacheResult {
 };
 
 struct ResourceLoader::Impl {
-    Impl(const ResourceConfiguration& config) :
+    explicit Impl(const ResourceConfiguration& config) :
         mEngine(config.engine),
         mNormalizeSkinningWeights(config.normalizeSkinningWeights),
         mGltfPath(config.gltfPath ? config.gltfPath : ""),
         mUriDataCache(std::make_shared<UriDataCache>()) {}
 
     Engine* const mEngine;
-    const bool mNormalizeSkinningWeights;
-    const std::string mGltfPath;
+    bool mNormalizeSkinningWeights;
+    std::string mGltfPath;
 
     // User-provided resource data with URI string keys, populated with addResourceData().
     // This is used on platforms without traditional file systems, such as Android, iOS, and WebGL.
@@ -320,6 +320,11 @@ ResourceLoader::~ResourceLoader() {
     delete pImpl;
 }
 
+void ResourceLoader::setConfiguration(const ResourceConfiguration& config) {
+    pImpl->mNormalizeSkinningWeights = config.normalizeSkinningWeights;
+    pImpl->mGltfPath = config.gltfPath;
+}
+
 void ResourceLoader::addResourceData(const char* uri, BufferDescriptor&& buffer) {
     pImpl->addResourceData(uri, std::move(buffer));
 }