Small NaN related optimisation in RCTShadowText

Summary: NaN values can not be compared directly, so we have to use `isnan` function.

Reviewed By: mmmulani

Differential Revision: D5859761

fbshipit-source-id: bf99a1ae574cd820265bef0c2bd255b194c5dc3c

Libraries/Text/RCTShadowText.m

@@ -198,7 +198,7 @@ - (NSTextStorage *)buildTextStorageForWidth:(CGFloat)width widthMode:(YGMeasureM
 {
   if (
       _cachedTextStorage &&
-      width == _cachedTextStorageWidth &&
+      (width == _cachedTextStorageWidth || (isnan(width) && isnan(_cachedTextStorageWidth))) &&
       widthMode == _cachedTextStorageWidthMode &&
       _cachedEffectiveLayoutDirection == self.effectiveLayoutDirection
   ) {