templates: Don't check IsLineTerminator() if character is negative

test/mjsunit/regress/regress-455212.js

Index: test/mjsunit/regress/regress-455212.js
diff --git a/test/mjsunit/eval-typeof-non-existing.js b/test/mjsunit/regress/regress-455212.js
similarity index 88%
copy from test/mjsunit/eval-typeof-non-existing.js
copy to test/mjsunit/regress/regress-455212.js
index 8cc6d0bcd3310b71c87b7c2620ef2e38ad6ebc44..f2fd033c3d0836a60f603837af31cd2a96662562 100644
--- a/test/mjsunit/eval-typeof-non-existing.js
+++ b/test/mjsunit/regress/regress-455212.js
@@ -28,8 +28,6 @@
 // Typeof expression must resolve to 'undefined' when it used on a
 // non-existing property. It is *not* allowed to throw a
 // ReferenceError.
-assertEquals('undefined', typeof xxx);
-assertEquals('undefined', eval('typeof xxx'));
 
-assertThrows('typeof(true ? xxx : yyy)', ReferenceError);
-assertThrows('with ({}) { typeof(true ? xxx : yyy) }', ReferenceError);
+// eval("\u0060\u005c") is an unterminated template string (\u0060)
+assertThrows("\u0060\u005c", SyntaxError);