Multiline variables that contain command-like text cause a crash

[smathot]

Adding the following text to a notepad item will cause a TypeError:

draw textline center=1 color=white font_bold=no font_family=serif font_italic=no font_size=32 html=yes show_if=always text="OpenSesame 3.3 <i>Lentiform Loewenfeld</i>" x=0 y=0 z_index=0

This is because the text is interpreted as a draw command, rather than as part of a multiline string. This should be fixed in convertor.js.