fix event color patch (#3943)

frappe/patches/v8_5/patch_event_colors.py

@@ -2,6 +2,10 @@ from __future__ import unicode_literals
 import frappe
 
 def execute():
+
+	if not frappe.db.sql("SHOW COLUMNS FROM `tabEvent` LIKE 'color';"):
+		return
+
 	colors = ['red', 'green', 'blue', 'yellow', 'skyblue', 'orange']
 	hex_colors = ['#ffc4c4', '#cef6d1', '#d2d2ff', '#fffacd', '#d2f1ff', '#ffd2c2']