Clear old tree counter in map array on load of old savegames

See: https://github.com/OpenTTD/OpenTTD/pull/10018

src/saveload/afterload.cpp

@@ -4098,6 +4098,14 @@ bool AfterLoadGame()
 		}
 	}
 
+	if (SlXvIsFeatureMissing(XSLFI_NO_TREE_COUNTER)) {
+		for (TileIndex t = 0; t < map_size; t++) {
+			if (IsTileType(t, MP_TREES)) {
+				ClearOldTreeCounter(t);
+			}
+		}
+	}
+
 	InitializeRoadGUI();
 
 	/* This needs to be done after conversion. */

src/saveload/extended_ver_sl.cpp

@@ -175,6 +175,7 @@ const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ XSLFI_INDUSTRY_ANIM_MASK,     XSCF_IGNORABLE_ALL,       1,   1, "industry_anim_mask",        nullptr, nullptr, nullptr        },
 	{ XSLFI_NEW_SIGNAL_STYLES,      XSCF_NULL,                2,   2, "new_signal_styles",         nullptr, nullptr, "XBST,NSID"    },
 	{ XSLFI_SCRIPT_INT64,           XSCF_NULL,                1,   1, "script_int64",              nullptr, nullptr, nullptr        },
+	{ XSLFI_NO_TREE_COUNTER,        XSCF_IGNORABLE_ALL,       1,   1, "no_tree_counter",           nullptr, nullptr, nullptr        },
 	{ XSLFI_NULL, XSCF_NULL, 0, 0, nullptr, nullptr, nullptr, nullptr },// This is the end marker
 };
 

src/saveload/extended_ver_sl.h

@@ -127,6 +127,7 @@ enum SlXvFeatureIndex {
 	XSLFI_GRF_ROADSTOPS,                          ///< NewGRF road stops
 	XSLFI_INDUSTRY_ANIM_MASK,                     ///< Industry tile animation masking
 	XSLFI_NEW_SIGNAL_STYLES,                      ///< New signal styles
+	XSLFI_NO_TREE_COUNTER,                        ///< No tree counter
 
 	XSLFI_SCRIPT_INT64,                           ///< See: SLV_SCRIPT_INT64