Fix scala#4393 WIP

Min tests: `try { ??? } catch {}` (can be scripted) and `try { ??? } catch {`.

Author: Blaisorblade

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -1259,7 +1259,10 @@ object Parsers {
             if (in.token == CATCH) {
               val span = in.offset
               in.nextToken()
-              (expr(), span)
+              accept(LBRACE)
+              val res = (expr(), span)
+              accept(RBRACE)
+              res
             } else (EmptyTree, -1)
 
           handler match {