Added Y-wise asserts to signs.

This should help detect #1313's second case.

src/BlockEntities/SignEntity.cpp

@@ -15,6 +15,7 @@
 cSignEntity::cSignEntity(BLOCKTYPE a_BlockType, int a_X, int a_Y, int a_Z, cWorld * a_World) :
 	super(a_BlockType, a_X, a_Y, a_Z, a_World)
 {
+	ASSERT((a_Y >= 0) && (a_Y < cChunkDef::Height));
 }
 
 

src/Protocol/Protocol17x.cpp

@@ -1355,6 +1355,7 @@ void cProtocol172::SendUpdateBlockEntity(cBlockEntity & a_BlockEntity)
 void cProtocol172::SendUpdateSign(int a_BlockX, int a_BlockY, int a_BlockZ, const AString & a_Line1, const AString & a_Line2, const AString & a_Line3, const AString & a_Line4)
 {
 	ASSERT(m_State == 3);  // In game mode?
+	ASSERT((a_BlockY >= 0) && (a_BlockY < cChunkDef::Height));
 	
 	cPacketizer Pkt(*this, 0x33);
 	Pkt.WriteInt(a_BlockX);

src/WorldStorage/WSSAnvil.cpp

@@ -623,6 +623,8 @@ void cWSSAnvil::LoadBlockEntitiesFromNBT(cBlockEntityList & a_BlockEntities, con
 
 cBlockEntity * cWSSAnvil::LoadBlockEntityFromNBT(const cParsedNBT & a_NBT, int a_Tag, int a_BlockX, int a_BlockY, int a_BlockZ, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta)
 {
+	ASSERT((a_BlockY >= 0) && (a_BlockY < cChunkDef::Height));
+
 	// Load the specific BlockEntity type:
 	switch (a_BlockType)
 	{