Fixed issue magento#20157

Updated css file

Author: Govind Sharma

app/design/frontend/Magento/luma/Magento_CatalogSearch/web/css/source/_module.less

@@ -18,6 +18,20 @@
 //  _____________________________________________
 
 & when (@media-common = true) {
+    
+    .search{
+		.fieldset{
+			.control{
+				.addon{
+					input{
+						flex-basis: auto;
+						width: 100%;
+					}
+				}
+			}
+		}
+	}
+    
     .block-search {
         margin-bottom: 0;