fix(ios): app crashing while setPage is called in componentDidMount (#261)

Co-authored-by: Mateusz Wit <[email protected]>

Author: MateWW

example/ios/ViewpagerExample.xcodeproj/project.pbxproj

@@ -65,6 +65,7 @@
 			children = (
 				871719007ECC5EAD276C345C /* Pods-ViewpagerExample.debug.xcconfig */,
 				4D7192F03A36A017E887435B /* Pods-ViewpagerExample.release.xcconfig */,
+				20F357AD24636CDE00C146DC /* ViewpagerExample-Bridging-Header.h */,
 			);
 			path = Pods;
 			sourceTree = "<group>";
@@ -94,7 +95,6 @@
 				83CBBA001A601CBA00E9B192 /* Products */,
 				2D16E6871FA4F8E400B85C8A /* Frameworks */,
 				1CFFDEF7170271C97B8B7E5A /* Pods */,
-				20F357AD24636CDE00C146DC /* ViewpagerExample-Bridging-Header.h */,
 			);
 			indentWidth = 2;
 			sourceTree = "<group>";

ios/ReactNativePageView.m

@@ -155,6 +155,9 @@ - (void)setReactViewControllers:(NSInteger)index
                            with:(UIViewController *)controller
                       direction:(UIPageViewControllerNavigationDirection)direction
                        animated:(BOOL)animated {
+    if (self.reactPageViewController == nil) {
+        return;
+    }
     __weak ReactNativePageView *weakSelf = self;
     uint16_t coalescingKey = _coalescingKey++;