fix(bridge): Don't read JS properties without obtaining a lock

In `TNSArrayAdapter`'s `countByEnumeratingWithState` we need to
obtain a JS engine lock before accessing properties of the JS array(-like)
object.

Author: mbektchiev

src/NativeScript/ObjC/TNSArrayAdapter.mm

@@ -55,6 +55,9 @@ - (id)objectAtIndex:(NSUInteger)index {
 
 - (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState*)state objects:(id[])buffer count:(NSUInteger)len {
     RELEASE_ASSERT_WITH_MESSAGE([TNSRuntime runtimeForVM:self->_vm], "The runtime is deallocated.");
+
+    JSLockHolder lock(self->_execState);
+
     if (state->state == 0) { // uninitialized
         state->state = 1;
         state->mutationsPtr = reinterpret_cast<unsigned long*>(self);
@@ -67,7 +70,6 @@ - (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState*)state objects
     NSUInteger count = 0;
     state->itemsPtr = buffer;
 
-    JSLockHolder lock(self->_execState);
     while (count < len && currentIndex < length) {
         *buffer++ = toObject(self->_execState, self->_object->get(self->_execState, currentIndex));
         currentIndex++;