Cycles: Fix problems in the IES loader when rendering with no file selected

intern/cycles/blender/blender_shader.cpp

@@ -827,6 +827,9 @@ static ShaderNode *add_node(Scene *scene,
 				break;
 			case BL::ShaderNodeTexIES::mode_INTERNAL:
 				ies->ies = get_text_datablock_content(b_ies_node.ies().ptr);
+				if(ies->ies.empty()) {
+					ies->ies = "\n";
+				}
 				break;
 		}
 		node = ies;

intern/cycles/blender/blender_util.h

@@ -468,7 +468,7 @@ static inline string blender_absolute_path(BL::BlendData& b_data,
 	return path;
 }
 
-static inline string get_text_datablock_content(const PointerRNA&& ptr)
+static inline string get_text_datablock_content(const PointerRNA& ptr)
 {
 	if(ptr.data == NULL) {
 		return "";

intern/cycles/render/light.cpp

@@ -891,8 +891,10 @@ void LightManager::tag_update(Scene * /*scene*/)
 int LightManager::add_ies_from_file(ustring filename)
 {
 	string content;
-	/* If the file can't be opened, call with an empty string */
-	path_read_text(filename.c_str(), content);
+	/* If the file can't be opened, call with an empty line */
+	if(filename.empty() || !path_read_text(filename.c_str(), content)) {
+		content == "\n";
+	}
 
 	return add_ies(ustring(content));
 }

intern/cycles/util/util_ies.cpp

@@ -109,6 +109,10 @@ public:
 
 bool IESFile::parse(ustring ies)
 {
+	if(ies.empty()) {
+		return false;
+	}
+
 	IESTextParser parser(ies);
 	if(parser.eof()) {
 		return false;