[iOS] Fixes text input plugin crash (flutter#20127)

Author: LongCatIsLooong

shell/platform/darwin/ios/framework/Source/FlutterTextInputPlugin.mm

@@ -387,8 +387,8 @@ - (void)dealloc {
 }
 
 - (UITextField*)textField {
-  if (_textField == nil) {
-    _textField = [[[UITextField alloc] init] autorelease];
+  if (!_textField) {
+    _textField = [[UITextField alloc] init];
   }
   return _textField;
 }

shell/platform/darwin/ios/framework/Source/FlutterTextInputPluginTest.m

@@ -17,6 +17,10 @@ - (void)setTextInputState:(NSDictionary*)state;
 - (BOOL)isVisibleToAutofill;
 @end
 
+@interface FlutterSecureTextInputView : FlutterTextInputView
+@property(nonatomic, strong) UITextField* textField;
+@end
+
 @interface FlutterTextInputPlugin ()
 @property(nonatomic, strong) FlutterTextInputView* reusableInputView;
 @property(nonatomic, assign) FlutterTextInputView* activeView;
@@ -496,4 +500,15 @@ - (void)testUITextInputCallsUpdateEditingStateOnce {
   [inputView unmarkText];
   XCTAssertEqual(updateCount, 6);
 }
+
+- (void)testNoZombies {
+  // Regression test for https://github.com/flutter/flutter/issues/62501.
+  FlutterSecureTextInputView* passwordView = [[FlutterSecureTextInputView alloc] init];
+
+  @autoreleasepool {
+    // Initialize the lazy textField.
+    [passwordView.textField description];
+  }
+  XCTAssert([[passwordView.textField description] containsString:@"TextField"]);
+}
 @end