get rid of weird nil check on CGFloat

Summary:
Changelog: [Internal]

this doesn't really make any sense, first of all CGFloat is a primitive data type so comparing it against nil only will return true if it's 0. but that won't catch cases where CGFloat is uninitialized bc it will be holding junk in memory.

the error checking of the value is already handled in the accessibility manager, so just remove it here.

Reviewed By: p-sun

Differential Revision: D34909365

fbshipit-source-id: 483f9c100433f8533edd784622523c5469c616c2

React/CoreModules/RCTDeviceInfo.mm

@@ -108,8 +108,9 @@ static BOOL RCTIsIPhoneX()
  RCTAssertMainQueue();
  RCTDimensions dimensions;
  if (moduleRegistry) {
- dimensions = RCTGetDimensions(
- ((RCTAccessibilityManager *)[moduleRegistry moduleForName:"AccessibilityManager"]).multiplier ?: 1.0);
+ RCTAccessibilityManager *accessibilityManager =
+ (RCTAccessibilityManager *)[moduleRegistry moduleForName:"AccessibilityManager"];
+ dimensions = RCTGetDimensions(accessibilityManager ? accessibilityManager.multiplier : 1.0);
  } else {
  RCTAssert(false, @"ModuleRegistry must be set to properly init dimensions.");
  }