fix icon size

Summary: Icon size passed to a button was ignored.

Reviewed By: passy

Differential Revision: D10301573

fbshipit-source-id: 00117a35622bbd490b74359f52ecc07929390205

src/ui/components/Button.js

@@ -326,7 +326,7 @@ class Button extends React.Component<
       iconComponent = (
         <Icon
           name={icon}
-          size={iconSize || this.props.compact === true ? 12 : 16}
+          size={iconSize || (this.props.compact === true ? 12 : 16)}
           color={color}
           variant={iconVariant || 'filled'}
           hasText={Boolean(children)}