skip dismiss all if all rows are hidden (#19564)

Summary:
Small fix based on
https://github.com/facebook/react-native/pull/19501#issuecomment-394486884

No need to mention it

[GENERAL] [BUGFIX] [YellowBox] - Message
Closes https://github.com/facebook/react-native/pull/19564

Differential Revision: D8276808

Pulled By: hramos

fbshipit-source-id: 59832d3d6e60ae30afbeb7c9303405746e9eec45

Libraries/ReactNative/YellowBox.js

@@ -424,7 +424,7 @@ class YellowBox extends React.Component<
     ];
     return (
       <View style={inspector ? styles.fullScreen : listStyle}>
-        {!inspector && (
+        {!inspector && rows.length > 0 && (
           <TouchableHighlight
             style={styles.dismissAllContainer}
             onPress={() => this.dismissWarning(null)}>