How to set Photoshop CC window size to 1280x720 via AppleScript?
I cannot replicate your problem as I don't own Adobe Photoshop, but it seems extremely likely that the process you're trying to tell s.th. to is NOT named "Adobe Photoshop CC".
(Did happen to me once, too ...)

My guess is supported by the fact that I could exactly reproduce your error messages by using "Safari" as placeholder but mis-spelling it "SafariX" in the script.
Try this command in Script-Editor (with Photoshop running) to find out:

tell application "System Events" to get processes whose ¬
name starts with "ph"