Added holder instanceof DoubleChest check to converter

src/main/java/ch/njol/skript/classes/data/DefaultConverters.java

@@ -176,6 +176,14 @@ public DefaultConverters() {}
 				return ((Block) holder).getLocation();
 			if (holder instanceof BlockState)
 				return BlockUtils.getLocation(((BlockState) holder).getBlock());
+			if (holder instanceof DoubleChest) {
+				DoubleChest doubleChest = (DoubleChest) holder;
+				if (doubleChest.getLeftSide() != null) {
+					return BlockUtils.getLocation(((BlockState) doubleChest.getLeftSide()).getBlock());
+				} else if (((DoubleChest) holder).getRightSide() != null) {
+					return BlockUtils.getLocation(((BlockState) doubleChest.getRightSide()).getBlock());
+				}
+			}
 			return null;
 		});
 

src/test/skript/tests/regressions/6811-inventory-holder-location-doublechest.sk

@@ -0,0 +1,20 @@
+test "inventory holder location double chest":
+	set {_b::1} to the block at spawn of world "world"
+	set {_b::2} to the block north of {_b::1}
+	set {_prev::1} to type of block at {_b::1}
+	set {_prev::2} to type of block at {_b::2}
+
+	set block at {_b::1} to chest[facing=east;type=right]
+	set block at {_b::2} to chest[facing=east;type=left]
+
+	set {_inv} to inventory of {_b::1}
+	set {_holder} to holder of {_inv}
+
+	set {_a-loc} to location of {_holder}
+	set {_b-loc::*} to location of {_b::1} and location of {_b::2}
+
+	# clean up first in case assert fails
+	set block at {_b::1} to {_prev::1}
+	set block at {_b::2} to {_prev::2}
+
+	assert {_b-loc::*} contains {_a-loc} with "holder location of double chest differs from block location"