fix background image issue

scss/mixins/_functions.scss

@@ -51,7 +51,7 @@ $color-modes: array-append((transparent), $css-default-modes);
 
 @function string-starts-with($h, $n) {
   @if is-string($h) and is-string($n) {
-    @return str-slice($h, 1, str-length($n)) == $n;
+    @return str-slice($h, 1, str-length($n))==$n;
   }
 
   @warn '`haystack: #{$h}` and `needle: #{$n}` are not valid strings';
@@ -72,7 +72,7 @@ $color-modes: array-append((transparent), $css-default-modes);
     $h-length: str-length($h);
     $n-length: str-length($n);
 
-    @return str-slice($h, $h-length - $n-length, $n-length) == $n;
+    @return str-slice($h, $h-length - $n-length, $n-length)==$n;
   }
 
   @warn '`haystack: #{$h}` and `needle: #{$n}` are not valid strings';
@@ -87,7 +87,7 @@ $color-modes: array-append((transparent), $css-default-modes);
       $url: str-slice($u, 5, str-length($u) - 1);
     }
 
-    @if string-starts-with($url, '../') or string-starts-with($url, 'http') {
+    @if string-starts-with($url, '../') or string-starts-with($url, '/') or string-starts-with($url, 'http') {
       @return true;
     }
   }