Bundle check (#1119)

* Check for NSBundle type before sending message

It seems the given `bundle` object may not be an NSBundle at times (appears to be capable of being at least an NSString), so we check to ensure the given parameter is of the expected type before we attempt to send a message with a potentially unkown selector.

* If we encounter an unloaded bundle, log it.

Parse/Internal/Object/Subclassing/PFObjectSubclassingController.m

@@ -332,7 +332,7 @@ - (void)_rawRegisterSubclass:(Class)kls {
 
 - (void)_registerSubclassesInLoadedBundle:(NSBundle *)bundle {
     // Skip bundles that aren't loaded yet.
-    if (!bundle.loaded || !bundle.executablePath) {
+    if (![bundle isKindOfClass:NSBundle.class] || !bundle.loaded || !bundle.executablePath) {
         return;
     }
     // Filter out any system bundles
@@ -343,7 +343,7 @@ - (void)_registerSubclassesInLoadedBundle:(NSBundle *)bundle {
 }
 
 - (void)_registerSubclassesInBundle:(NSBundle *)bundle {
-    PFConsistencyAssert(bundle.loaded, @"Cannot register subclasses in a bundle that hasn't been loaded!");
+    PFConsistencyAssert(bundle.loaded, @"Cannot register subclasses in an unloaded bundle: %@", bundle);
 
     const char *executablePath = bundle.executablePath.UTF8String;
     if (executablePath == NULL) {