Fixed conflicting variable names in readPropertyForNode:parent:isExtraProp:

[richard-sim]

readPropertyForNode:parent:isExtraProp: has variables named 'type' declared at both the outermost level, and nested within; this will cause build warnings/errors if HiddenLocalVariables warning is turned on in the project settings. The warning's description makes it sound like it's alerting you to the fact that you are getting unintended behaviour - so I fixed it.