Fixes #11402: Set width: auto; to select.form-control within .form-inline

less/forms.less

@@ -309,6 +309,11 @@ input[type="checkbox"],
       display: inline-block;
     }
 
+    // Override `width: 100%;` when not within a `.form-group`
+    select.form-control {
+      width: auto;
+    }
+
     // Remove default margin on radios/checkboxes that were used for stacking, and
     // then undo the floating of radios and checkboxes to match (which also avoids
     // a bug in WebKit: https://github.com/twbs/bootstrap/issues/1969).