Qt: reset columns when applying a display filter

Bug: 11786
Change-Id: I7d3b4139328adaf2f79f008a8772b3182c1eb1f0
Reviewed-on: https://code.wireshark.org/review/12688
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>
Reviewed-by: Stig Bjørlykke <stig@bjorlykke.org>

ui/qt/main_window_slots.cpp

@@ -290,6 +290,9 @@ void MainWindow::filterPackets(QString new_filter, bool force)
     } else {
         emit displayFilterSuccess(false);
     }
+    if (packet_list_) {
+        packet_list_->resetColumns();
+    }
 }
 
 // A new layout should be applied when it differs from the old layout AND