Setting font bold causes errrors in QQmlApplicationEngine

adding in a text box and click on the B  in the "emphasis field" on the IDE will set 

Text { ........... font.bold: "true" }

a when run this will cause the error: Invalid property assignment: boolean expected

unchecking this box sets it to Text { ........... font.bold: "false" }

which fails with the same error. remove this setting and using the IDE to set "font weight" to bold  will set  Text { ........... font.weight: font.bold }

and the compile passes with no errors.