Erroneous check for options=false in destroy method.

Because the responsive method mutates the _.options object, the check for
_.options.arrows in the destroy method was actually always opposite to the
truth when the arrows value changes as it was taking the value from the
previous breakpoint.

Fixed.

fixes #1536 - @wjthomas9
#1536 (comment)

slick/slick.js

@@ -827,34 +827,33 @@
             _.$dots.remove();
         }
 
-        if ( _.options.arrows === true ) {
 
-            if ( _.$prevArrow && _.$prevArrow.length ) {
+        if ( _.$prevArrow && _.$prevArrow.length ) {
 
-                _.$prevArrow
-                    .removeClass('slick-disabled slick-arrow slick-hidden')
-                    .removeAttr('aria-hidden aria-disabled tabindex')
-                    .css("display","");
+            _.$prevArrow
+                .removeClass('slick-disabled slick-arrow slick-hidden')
+                .removeAttr('aria-hidden aria-disabled tabindex')
+                .css("display","");
 
-                if ( _.htmlExpr.test( _.options.prevArrow )) {
-                    _.$prevArrow.remove();
-                }
+            if ( _.htmlExpr.test( _.options.prevArrow )) {
+                _.$prevArrow.remove();
             }
+        }
 
-            if ( _.$nextArrow && _.$nextArrow.length ) {
+        if ( _.$nextArrow && _.$nextArrow.length ) {
 
-                _.$nextArrow
-                    .removeClass('slick-disabled slick-arrow slick-hidden')
-                    .removeAttr('aria-hidden aria-disabled tabindex')
-                    .css("display","");
+            _.$nextArrow
+                .removeClass('slick-disabled slick-arrow slick-hidden')
+                .removeAttr('aria-hidden aria-disabled tabindex')
+                .css("display","");
 
-                if ( _.htmlExpr.test( _.options.nextArrow )) {
-                    _.$nextArrow.remove();
-                }
+            if ( _.htmlExpr.test( _.options.nextArrow )) {
+                _.$nextArrow.remove();
             }
-
+            
         }
 
+
         if (_.$slides) {
 
             _.$slides