Remove previously scheduled NetInfo callbacks if they haven't fired

Summary:
@public
If you call NetInfo.getCurrentConnectivity multiple times in succession, we'll create a bunch of callbacks but lose them in the ether.
With this fix, we'll unschedule them before creating a new one, which should resolve some crashes we're seeing.

Reviewed By: PeteTheHeat

Differential Revision: D10409486

fbshipit-source-id: 6065b09fa626f7f06aed9bf0e278c0a6a6169f58

Libraries/Network/RCTNetInfo.m

@@ -110,6 +110,8 @@ - (void)dealloc
   if (_firstTimeReachability) {
     SCNetworkReachabilityUnscheduleFromRunLoop(self->_firstTimeReachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
     CFRelease(self->_firstTimeReachability);
+    _firstTimeReachability = nil;
+    _resolve = nil;
   }
 }
 
@@ -184,6 +186,12 @@ - (BOOL)setReachabilityStatus:(SCNetworkReachabilityFlags)flags
 RCT_EXPORT_METHOD(getCurrentConnectivity:(RCTPromiseResolveBlock)resolve
                   reject:(__unused RCTPromiseRejectBlock)reject)
 {
+  if (_firstTimeReachability) {
+    SCNetworkReachabilityUnscheduleFromRunLoop(self->_firstTimeReachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
+    CFRelease(self->_firstTimeReachability);
+    _firstTimeReachability = nil;
+    _resolve = nil;
+  }
   _firstTimeReachability = [self getReachabilityRef];
   _resolve = resolve;
 }