Fix parseInt when passing empty string.

Before allocating buffer for the string first
we check that the length of it is greater then 0.
If not then the result is a NaN.

JerryScript-DCO-1.0-Signed-off-by: Peter Gal pgal.u-szeged@partner.samsung.com

tests/jerry/global-parseint.js

@@ -27,6 +27,7 @@ assert(parseInt("ABC", 16) === 2748);
 assert(parseInt("12A3") === 12);
 assert(parseInt("12.34") === 12);
 assert(isNaN(parseInt("AB")));
+assert(isNaN(parseInt("")));
 
 var bool = true;
 var obj = new Object();