diff --git a/update-chunkymap-on-ubuntu-from-web.sh b/update-chunkymap-on-ubuntu-from-web.sh
index 1d0983a..b56c4ac 100644
--- a/update-chunkymap-on-ubuntu-from-web.sh
+++ b/update-chunkymap-on-ubuntu-from-web.sh
@@ -19,12 +19,12 @@ fi
 #sh "$CHUNKYMAP_INSTALLER_DIR/update-chunkymap-installer-only.sh"
 if [ -f "$CHUNKYMAP_DEST/update-chunkymap-installer-only.sh" ]; then
 	sh "$CHUNKYMAP_DEST/update-chunkymap-installer-only.sh"
-	#further instructions are in separate file in case updater was updated:
+	#further instructions are in separate file in case updater was updated (sleep first otherwise file won't be finished writing):
 	sleep .25
 	sh "$CHUNKYMAP_DEST/post-update.sh"
 else
 	sh "$CHUNKYMAP_INSTALLER_DIR/update-chunkymap-installer-only.sh"
-	#further instructions are in separate file in case updater was updated:
+	#further instructions are in separate file in case updater was updated (sleep first otherwise file won't be finished writing):
 	sleep .25
 	sh "$CHUNKYMAP_INSTALLER_DIR/post-update.sh"
 fi
diff --git a/web/chunkymap.php b/web/chunkymap.php
index 5316af6..d562d95 100644
--- a/web/chunkymap.php
+++ b/web/chunkymap.php
@@ -1238,8 +1238,14 @@ function echo_chunkymap_canvas($show_player_names_enable, $decachunks_enable, $c
 					//done on each draw: last_bawidget.text = 
 					pen_y += size_1em_pixel_count + padding_h;
 					
-					document.getElementById("chunkymap_table").style.visibility="hidden";
-					document.getElementById("singleimage_table").style.visibility="hidden";
+					chunkymap_table = document.getElementById("chunkymap_table");
+					if (chunkymap_table!=null) {
+						chunkymap_table.style.visibility="hidden";
+					}
+					singleimage_table = document.getElementById("singleimage_table");
+					if (singleimage_table!=null) {
+						singleimage_table.style.visibility="hidden";
+					}
 					
 					process_zoom_change();
 					draw_map();