Set the token type after an invalid character error.

Otherwise, it still has the previous token's type. This can cause it
to get stuck in a loop in some places in the compiler.

Fix #428.

test/regression/428.wren

@@ -0,0 +1,6 @@
+// This was crashing the compiler with an out of bounds memory access.
+
+// expect error line 6
+// expect error line 7
+Fiber.new {
+     isDone ["", àààààààààààààààààààààààààààààààààààààààààààààààààà