check for existence of the columns beefore trying to add them

db/zm_update-1.26.0.sql

@@ -1,3 +1,27 @@
-ALTER TABLE `Monitors` ADD `Colours` TINYINT UNSIGNED NOT NULL DEFAULT '1' AFTER `Height`;
-ALTER TABLE `Monitors` ADD `Deinterlacing` INT UNSIGNED NOT NULL DEFAULT '0' AFTER `Orientation`;
+SET @s = (SELECT IF(
+    (SELECT COUNT(*)
+    FROM INFORMATION_SCHEMA.COLUMNS
+    WHERE table_name = 'Monitors'
+    AND table_schema = DATABASE()
+    AND column_name = 'Colours'
+    ) > 0,
+"SELECT 'Column Colours exists in Monitors'",
+"ALTER TABLE `Monitors` ADD `Colours` TINYINT UNSIGNED NOT NULL DEFAULT '1' AFTER `Height`"
+));
 
+PREPARE stmt FROM @s;
+EXECUTE stmt;
+
+SET @s = (SELECT IF(
+    (SELECT COUNT(*)
+    FROM INFORMATION_SCHEMA.COLUMNS
+    WHERE table_name = 'Monitors'
+    AND table_schema = DATABASE()
+    AND column_name = 'Deinterlacing'
+    ) > 0,
+"SELECT 'Column Deinterlacing exists in Monitors'",
+"ALTER TABLE `Monitors` ADD `Deinterlacing` INT UNSIGNED NOT NULL DEFAULT '0' AFTER `Orientation`"
+));
+
+PREPARE stmt FROM @s;
+EXECUTE stmt;