Wrong bounds calculation for alt block when section split is used

[tomazas]

Hi,

SVG/PNG is generated incorrectly for alt blocks if section split line "===" is used in sequence diagram.
Example:

autonumber
alt Secondary attach
Device <- "Server": HTTPS 200 OK: Show page
Device -> "Server": HTTPS POST /success: Accept
Device <- Device: JS verify pending status
"Server" -> "SM": HTTPS POST: confirm1
"Server" <- "SM": HTTPS 200 OK: deploy page
"Server" -> "SM": HTTPS POST: confirm2
"Server" <- "SM": HTTPS 200 OK: [matchingID] = confirm2()
====
"Server" -> "SS": provision(params...)
"Server" <- "SS": success = provision()
alt On success
Device <- "Server": HTTPS 200 OK: JS callback) // Show success page
====
Device -> "SS": "initAuth"
else On error
Device <- "Server": HTTPS 200 OK: Show error / failure page
end
Device <- Device: done // completed flow ends
end
@enduml