jscript: Correctly handle -1 index in regexp match result.

dlls/jscript/regexp.c

@@ -3349,8 +3349,13 @@ static HRESULT do_regexp_match_next(script_ctx_t *ctx, RegExpInstance *regexp, c
         *parens_cnt = regexp->jsregexp->parenCount;
 
         for(i=0; i < regexp->jsregexp->parenCount; i++) {
-            (*parens)[i].str = *cp + result->parens[i].index;
-            (*parens)[i].len = result->parens[i].length;
+            if(result->parens[i].index == -1) {
+                (*parens)[i].str = NULL;
+                (*parens)[i].len = 0;
+            }else {
+                (*parens)[i].str = *cp + result->parens[i].index;
+                (*parens)[i].len = result->parens[i].length;
+            }
         }
     }
 

dlls/jscript/tests/regexp.js

@@ -71,6 +71,11 @@ m = re.exec();
 ok(m === null, "m is not null");
 ok(re.lastIndex === 0, "re.lastIndex = " + re.lastIndex);
 
+m = /(a|b)+|(c)/.exec("aa");
+ok(m[0] === "aa", "m[0] = " + m[0]);
+ok(m[1] === "a", "m[1] = " + m[1]);
+ok(m[2] === "", "m[2] = " + m[2]);
+
 b = re.test("  a ");
 ok(b === true, "re.test('  a ') returned " + b);
 ok(re.lastIndex === 3, "re.lastIndex = " + re.lastIndex);