Don't apply empty attributed string for TextInput (#25143)

Summary:
Issue reported by Titozzz , `TextInput` would shrink when we have attributes like `lineHeight`.
Demonstration can see GIF like below:
https://giphy.com/gifs/KGNs1qIMHF3DIk1EPK

I think the reason is we apply an empty attributed string to `UITextField`, now if the length is 0, we just nil the `attributedText` instead.

## Changelog

[iOS] [Fixed] - Don't apply empty attributed string for TextInput
Pull Request resolved: #25143

Differential Revision: D15661751

Pulled By: sammy-SC

fbshipit-source-id: 9770484a1b68a6409e63ea25ac9a6fd0d3589b14

Libraries/Text/TextInput/RCTBaseTextInputShadowView.m

@@ -174,7 +174,12 @@ - (void)uiManagerWillPerformMounting
     baseTextInputView.reactPaddingInsets = paddingInsets;
 
     if (isAttributedTextChanged) {
-      baseTextInputView.attributedText = attributedText;
+      // Don't set `attributedText` if length equal to zero, otherwise it would shrink when attributes contain like `lineHeight`.
+      if (attributedText.length != 0) {
+        baseTextInputView.attributedText = attributedText;
+      } else {
+        baseTextInputView.attributedText = nil;
+      }
     }
   }];
 }

Libraries/Text/TextInput/RCTBaseTextInputView.h

@@ -46,7 +46,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, assign) BOOL secureTextEntry;
 @property (nonatomic, copy) RCTTextSelection *selection;
 @property (nonatomic, strong, nullable) NSNumber *maxLength;
-@property (nonatomic, copy) NSAttributedString *attributedText;
+@property (nonatomic, copy, nullable) NSAttributedString *attributedText;
 @property (nonatomic, copy) NSString *inputAccessoryViewID;
 @property (nonatomic, assign) UIKeyboardType keyboardType;