fix #3849 -- side chat: this.input_ref.current.focus is not a function
fix #3849 -- side chat: this.input_ref.current.focus is not a function

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