Set default background-color for Select

Signed-off-by: Alex Andreev <alex.andreev.email@gmail.com>

src/renderer/components/+namespaces/namespace-select-filter.scss

@@ -1,9 +1,9 @@
 .NamespaceSelectFilter {
-  --gradientColor: var(--contentColor);
+  --gradientColor: var(--select-menu-bgc);
 
   .Select {
     &.theme-light {
-      --gradientColor: #fff;
+      --gradientColor: white;
     }
 
     &__placeholder {

src/renderer/components/select/select.scss

@@ -35,8 +35,6 @@ html {
     position: relative;
     min-width: 220px;
 
-    
-
     * {
       color: inherit;
     }
@@ -50,7 +48,7 @@ html {
     &__control {
       border: none;
       border-radius: $radius;
-      background: transparent;
+      background: var(--select-menu-bgc);
       min-height: 0;
       box-shadow: 0 0 0 1px $halfGray;
       cursor: pointer;