[regex] avoid an unnecessary comparison

when the index is op is used, it always returns -1 for start indexes
beyond the string length

src/vm/parrot/QAST/Compiler.nqp

@@ -1568,7 +1568,9 @@ class QAST::Compiler is HLL::Compiler {
             $ops.push_pirop('index', %*REG<pos>, %*REG<tgt>, self.rxescape($node[0]), %*REG<pos>);
             $ops.push_pirop('eq', %*REG<pos>, -1, %*REG<fail>);
         }
-        $ops.push_pirop('gt', %*REG<pos>, %*REG<eos>, %*REG<fail>);
+        else {
+            $ops.push_pirop('gt', %*REG<pos>, %*REG<eos>, %*REG<fail>);
+        }
         $ops.push_pirop('repr_bind_attr_int', %*REG<cur>, %*REG<curclass>, '"$!from"', %*REG<pos>);
         $ops.push($scanlabel);
         self.regex_mark($ops, $looplabel, %*REG<pos>, 0);