BBuffer: initialize variables and cleanup

* Restore the BSmallBuffer exception in constructor,
  it's not actually implemented or used but it should
  still be keep safe.
* Initialize some variables in BBuffer and BBufferGroup.

src/kits/media/Buffer.cpp

@@ -190,17 +190,21 @@ BBuffer::BBuffer(const buffer_clone_info& info)
 	fBufferList(NULL),
 	fArea(-1),
 	fData(NULL),
-	fSize(0)
+	fOffset(0),
+	fSize(0),
+	fFlags(0)
 {
 	CALLED();
 
-	// Must be -1 if not registered
-	fMediaHeader.buffer = -1;
-
+	// Ensure that the media_header is clean
+	memset(&fMediaHeader, 0, sizeof(fMediaHeader));
 	// special case for BSmallBuffer
 	if (info.area == 0 && info.buffer == 0)
 		return;
 
+	// Must be -1 if registration fail
+	fMediaHeader.buffer = -1;
+
 	fBufferList = BPrivate::SharedBufferList::Get();
 	if (fBufferList == NULL) {
 		ERROR("BBuffer::BBuffer: BPrivate::SharedBufferList::Get() failed\n");

src/kits/media/SharedBufferList.cpp

@@ -25,9 +25,9 @@
 #include <DataExchange.h>
 
 
-static BPrivate::SharedBufferList* sList;
-static area_id sArea;
-static int32 sRefCount;
+static BPrivate::SharedBufferList* sList = NULL;
+static area_id sArea = -1;
+static int32 sRefCount = 0;
 static BLocker sLocker("shared buffer list");
 
 
@@ -419,6 +419,7 @@ SharedBufferList::_Init()
 	for (int32 i = 0; i < kMaxBuffers; i++) {
 		fInfos[i].id = -1;
 	}
+	fCount = 0;
 
 	return B_OK;
 }