iOS: silence compiler warning about unimplemented 'selectionRectsForRange'

Implement a dummy method to silence the compiler.
After testing, this method seems to never be called. Which is
good, since the current IM API in Qt have little to offer to resolve
what is being asked. Until a need arise, we just return
an empty array.

Change-Id: I573eb8205a7e635a46d487ae175fb46e3a602001
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@theqtcompany.com>

src/plugins/platforms/ios/qiostextresponder.mm

@@ -738,6 +738,15 @@
     return toCGRect(startRect.united(endRect));
 }
 
+- (NSArray *)selectionRectsForRange:(UITextRange *)range
+{
+    Q_UNUSED(range);
+    // This method is supposed to return a rectangle for each line with selection. Since we don't
+    // expose an API in Qt/IM for getting this information, and since we never seems to be getting
+    // a call from UIKit for this, we return an empty array until a need arise.
+    return [[NSArray new] autorelease];
+}
+
 - (CGRect)caretRectForPosition:(UITextPosition *)position
 {
     Q_UNUSED(position);