Wrap the body of parse_command() in a try/catch to turn errors into warnings

As requested by Keyop in #synchrob0yyz

exec/imapservice.js

@@ -647,6 +647,7 @@ function handle_command(command, args, defs)
 
 function parse_command(line)
 {
+	try {
 		function execute_line(args) {
 			if(args.length >= 2) {
 				command=args[1].toUpperCase();
@@ -771,6 +772,9 @@ function parse_command(line)
 
 		send_updates();
 		return(execute_line(parse_line()));
+	} catch(error) {
+		log(LOG_WARNING, "Exception during command parsing: " + error);
+	}
 }
 
 // Command handling functions