Remove error condition from get_global_transform()

(cherry picked from commit 2ff676a696a9cc1d77c0a8f4d5f31de8c7b5bc1a)

doc/classes/CanvasItem.xml

@@ -301,7 +301,7 @@
 		<method name="get_global_transform" qualifiers="const">
 			<return type="Transform2D" />
 			<description>
-				Returns the global transform matrix of this item.
+				Returns the global transform matrix of this item, i.e. the combined transform up to the topmost [CanvasItem] node. The topmost item is a [CanvasItem] that either has no parent, has non-[CanvasItem] parent or it is top-level. See also [method set_as_toplevel].
 			</description>
 		</method>
 		<method name="get_global_transform_with_canvas" qualifiers="const">

scene/2d/canvas_item.cpp

@@ -475,9 +475,6 @@ Transform2D CanvasItem::get_global_transform_with_canvas() const {
 }
 
 Transform2D CanvasItem::get_global_transform() const {
-#ifdef DEBUG_ENABLED
-	ERR_FAIL_COND_V(!is_inside_tree(), get_transform());
-#endif
 	if (global_invalid) {
 		const CanvasItem *pi = get_parent_item();
 		if (pi) {