fix

src/function.scss

@@ -35,6 +35,7 @@
   
   // convert px to rem
   @function rem($size) {
+    $size : $size+ "";
     $remSize: math.div(to-number($size), 16);
     //Default font size on html is 16px;
     @return #{$remSize}rem;
@@ -42,12 +43,14 @@
   
   // convert px to em
   @function em($size) {
+    $size : $size+ "";
     $remSize: math.div(to-number($size), 16);
     @return #{$remSize}em;
   }
   
   // convert pt to rem
   @function pt-rem($size) {
+    $size : $size+ "";
     $pxSize:  to-number($size) * 1.328147;
     $remSize: $pxSize / 16;
     @return #{$remSize}rem;
@@ -55,6 +58,7 @@
   
   // convert pt to em
   @function pt-em($size) {
+    $size : $size+ "";
     $pxSize:  to-number($size) * 1.328147;
     $remSize: $pxSize / 16;
     @return #{$remSize}em;