webapp/course: fix TS1015: Parameter cannot have question mark and initializer.
webapp/course: fix TS1015: Parameter cannot have question mark and initializer.

sagemathinc/smc,sagemathinc/smc,DrXyzzy/smc,tscholl2/smc,sagemathinc/smc,tscholl2/smc,DrXyzzy/smc,sagemathinc/smc,DrXyzzy/smc,tscholl2/smc,tscholl2/smc,DrXyzzy/smc,tscholl2/smc