-fixes to ring buffer (fixes network error)

-fixes to invalid disabling of commands on scene tree dock

core/io/marshalls.cpp

@@ -36,7 +36,10 @@ Error decode_variant(Variant& r_variant,const uint8_t *p_buffer, int p_len,int *
 	const uint8_t * buf=p_buffer;
 	int len=p_len;
 
-	ERR_FAIL_COND_V(len<4,ERR_INVALID_DATA);
+	if (len<4) {
+
+		ERR_FAIL_COND_V(len<4,ERR_INVALID_DATA);
+	}
 
 
 	uint32_t type=decode_uint32(buf);

core/io/packet_peer.cpp

@@ -156,7 +156,6 @@ Error PacketPeerStream::_poll_buffer() const {
 	Error err = peer->get_partial_data(&temp_buffer[0], ring_buffer.space_left(), read);
 	if (err)
 		return err;
-
 	if (read==0)
 		return OK;
 
@@ -202,7 +201,7 @@ Error PacketPeerStream::get_packet(const uint8_t **r_buffer,int &r_buffer_size)
 	uint8_t lbuf[4];
 	ring_buffer.copy(lbuf,0,4);
 	remaining-=4;
-	uint32_t len = decode_uint32(lbuf);
+	uint32_t len = decode_uint32(lbuf);	
 	ERR_FAIL_COND_V(remaining<(int)len,ERR_UNAVAILABLE);
 
 	ring_buffer.read(lbuf,4); //get rid of first 4 bytes

core/ring_buffer.h

@@ -141,15 +141,15 @@ public:
 	inline int space_left() {
 		int left = read_pos - write_pos;
 		if (left < 0) {
-			return size() + left;
+			return size() + left - 1;
 		};
 		if (left == 0) {
-			return size();
+			return size()-1;
 		};
-		return left;
+		return left -1;
 	};
 	inline int data_left() {
-		return size() - space_left();
+		return size() - space_left() - 1;
 	};
 	
 	inline int size() {

tools/editor/scene_tree_dock.cpp

@@ -1088,7 +1088,8 @@ void SceneTreeDock::_delete_confirm() {
 void SceneTreeDock::_update_tool_buttons() {
 
 	Node *sel = scene_tree->get_selected();
-	bool disable = !sel || (sel!=edited_scene && sel->get_owner()!=edited_scene) || (edited_scene->get_scene_instance_state().is_valid() && edited_scene->get_scene_instance_state()->find_node_by_path(edited_scene->get_path_to(sel))>=0);
+	bool disable = !sel || (sel!=edited_scene && sel->get_owner()!=edited_scene);
+	disable = disable || (edited_scene->get_scene_inherited_state().is_valid() && edited_scene->get_scene_inherited_state()->find_node_by_path(edited_scene->get_path_to(sel))>=0);
 	bool disable_root = disable || sel->get_parent()==scene_root;
 	bool disable_edit = !sel;