fix deleting columns

app/Models/Proposal.php

@@ -137,9 +137,10 @@ class Proposal extends BaseModel
                 'proposal_id' => $this->getKey(),
                 'note' => $changeset->note,
                 'row_count' => 0, // Will be set later when we are sure about the row count
-                'columns' => array_map(function(Column $c) {
+                'columns' => array_filter(array_map(function(Column $c) {
+                    if ($c->toRemove) return null;
                     return $c->toArray(false);
-                }, $columns),
+                }, $columns)),
             ]);
 
             $newRevision->save(); // this gives it an ID, needed to associate rows