Fix rb_rescue2() to stop when seeing the (VALUE)0 argument

* The previous version of the spec would pass unintentionally due to
  (VALUE)0 == Qfalse and the rescue nodes raising
  TypeError (class or module required for rescue clause).

(cherry picked from commit be5f8cf)

Author: eregon

CHANGELOG.md

@@ -19,6 +19,7 @@ Bug fixes:
 * Fixed `SystemStackError` sometimes replaced by an internal Java `NoClassDefFoundError` on JVM (#1743).
 * Fixed constant/identifier detection in lexer for non-ASCII encodings (#2079, #2102, @ivoanjo).
 * Fixed parsing of `--jvm` as an application argument (#2108).
+* Fix `rb_rescue2` to ignore the end marker `(VALUE)0` (#2127, #2130).
 
 Compatibility:
 

src/main/c/cext/exception.c

@@ -85,6 +85,10 @@ VALUE rb_rescue2(VALUE (*b_proc)(ANYARGS), VALUE data1, VALUE (*r_proc)(ANYARGS)
   // arguments using the polyglot api.
   for (;n < total; n++) {
     VALUE arg = polyglot_get_arg(n);
+    if (arg == (VALUE)0) {
+      break;
+    }
+
     rb_ary_push(rescued, arg);
   }
   return cext_rb_rescue2(b_proc, data1, r_proc, data2, rb_tr_unwrap(rescued));