Fix TextInput text color not applying

Summary:
Setting the color for a TextInput with nodes was broken. The text color was
not being applied due to an optimization that prevented setting spans if
begin and end were the same (which is the case for an empty TextInput).
This patch depends on D2962643.

Differential Revision: D2962394

ReactAndroid/src/main/java/com/facebook/react/flat/RCTTextInput.java

@@ -140,6 +140,11 @@ public class RCTTextInput extends RCTVirtualText implements AndroidView, CSSNode
     mPaddingChanged = false;
   }
 
+  @Override
+  boolean shouldAllowEmptySpans() {
+    return true;
+  }
+
   /**
    * Returns a new CharSequence that includes all the text and styling information to create Layout.
    */