fix(ios): make Ti.UI.PickerColumn.rowCount NSNumber*, not NSInteger

theoretically this should avoid crash

iphone/Classes/TiUIPicker.m

@@ -330,7 +330,7 @@ - (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
 - (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
 {
   TiUIPickerColumnProxy *proxy = [[self columns] objectAtIndex:component];
-  return [proxy rowCount];
+  return proxy.rowCount.integerValue;
 }
 
 #pragma mark Delegates (only for UIPickerView)

iphone/Classes/TiUIPickerColumnProxy.h

@@ -14,12 +14,12 @@
 }
 
 @property (nonatomic, readonly) NSMutableArray *rows;
-@property (nonatomic, readonly) NSInteger rowCount;
+@property (nonatomic, readonly) NSNumber *rowCount;
 @property (nonatomic, readwrite, assign) NSInteger column;
 
 - (NSNumber *)addRow:(id)row;
 - (void)removeRow:(id)row;
-- (id)rowAt:(NSInteger)row;
+- (id)rowAt:(NSUInteger)row;
 
 @end
 #endif

iphone/Classes/TiUIPickerColumnProxy.m

@@ -31,12 +31,12 @@ - (NSMutableArray *)rows
   return [[rows copy] autorelease];
 }
 
-- (NSInteger)rowCount
+- (NSNumber *)rowCount
 {
-  return [rows count];
+  return NUMUINTEGER((rows != nil) ? rows.count : 0);
 }
 
-- (id)rowAt:(NSInteger)index
+- (id)rowAt:(NSUInteger)index
 {
   return (index < [rows count]) ? [rows objectAtIndex:index] : nil;
 }

iphone/Classes/TiUIPickerProxy.m

@@ -83,7 +83,8 @@ - (void)windowWillOpen
   // Tell all of the picker bits that their window has opened.  Can't operate
   // on the rows array directly; they're returned as a copy from the column.
   for (TiUIPickerColumnProxy *column in [self columns]) {
-    for (NSInteger i = 0; i < [column rowCount]; i++) {
+    NSUInteger rowCount = column.rowCount.unsignedIntegerValue;
+    for (NSUInteger i = 0; i < rowCount; i++) {
       [[column rowAt:i] windowWillOpen];
     }
   }
@@ -138,7 +139,8 @@ - (void)addPickerColumn:(NSDictionary *)params
   NSMutableArray *columns = [params objectForKey:@"columns"];
   TiUIPickerColumnProxy *column = [params objectForKey:@"column"];
   if (windowOpened) {
-    for (NSInteger i = 0; i < [column rowCount]; i++) {
+    NSUInteger rowCount = column.rowCount.unsignedIntegerValue;
+    for (NSUInteger i = 0; i < rowCount; i++) {
       TiUIPickerRowProxy *row = [column rowAt:i];
 
       [row windowWillOpen];
@@ -154,10 +156,13 @@ - (void)addRowOfColumns:(NSDictionary *)params
 {
   ENSURE_UI_THREAD_1_ARG(params);
   NSMutableArray *columns = [params objectForKey:@"columns"];
-  NSArray *data = [params objectForKey:@"data"];
-  for (id column in data) {
+  NSArray<TiUIPickerColumnProxy *> *data = [params objectForKey:@"data"];
+  for (TiUIPickerColumnProxy *column in data) {
     if (windowOpened) {
-      for (NSInteger i = 0; i < [column rowCount]; i++) {
+      ENSURE_TYPE(column, TiUIPickerColumnProxy);
+
+      NSUInteger rowCount = column.rowCount.unsignedIntegerValue;
+      for (NSUInteger i = 0; i < rowCount; i++) {
         TiUIPickerRowProxy *row = [column rowAt:i];
 
         [row windowWillOpen];