Bug Fix - App crashes on new start chat.

Vector/ViewController/ContactsTableViewController.m

@@ -133,6 +133,8 @@
     
     userContact = nil;
     
+    forceSearchResultRefresh = NO;
+    
     searchProcessingQueue = nil;
     searchProcessingLocalContacts = nil;
     searchProcessingMatrixContacts = nil;
@@ -299,6 +301,12 @@
         
         dispatch_sync(dispatch_get_main_queue(), ^{
             
+            // Sanity check: check whether self has been destroyed.
+            if (!searchProcessingQueue)
+            {
+                return;
+            }
+            
             // Render the search result only if there is no other search in progress.
             searchProcessingCount --;