When the text has missing characters in the font ("?" or "!") the canvas resorts back to the system default, but when used with the "destination-in" or "source-in" operation the text doesn't render.

Working with valid characters (Destination-in):
Text:

Invalid Characters present (Destination-in):
Text:

Working with valid characters (Source-Over):
Text:

Working with invalidcharacters (Source-Over):
Text: