- add missing initialization of several class members

- prefer check for empty() over check for size() in OptimizeGraph (empty() is guaranteed to be constant time, size() is not)
- fix a couple of incorrect indentations

code/BaseImporter.cpp

@@ -480,7 +480,9 @@ namespace Assimp
 struct Assimp::BatchData
 {
 	BatchData()
-		:	next_id(0xffff)
+        : pIOSystem()
+        , pImporter()
+        , next_id(0xffff)
 	{}
 
 	// IO system to be used for all imports