Preserve separator at start of variable from QuotedFragment skipped chars

lib/liquid/variable.rb

@@ -100,7 +100,9 @@ module Liquid
         new_filter_markup = Utils.match_captures_replace(filters_match, 1 => new_filters_markup)
       end
 
-      Utils.match_captures_replace(markup_match, 1 => new_name_markup, 2 => new_filter_markup)
+      new_markup = Utils.match_captures_replace(markup_match, 1 => new_name_markup, 2 => new_filter_markup)
+      new_markup.prepend(" ") if markup_match.begin(0) > 0
+      new_markup
     end
 
     def self.lax_migrate_filter_argument(unparsed_arg)

test/unit/migrate_unit_test.rb

@@ -29,7 +29,8 @@ class MigrateUnitTest < Minitest::Test
     with_error_mode(:lax) do
       assert_migration({
         %({{ ,|"' }}) => "{{  }}", # no MarkupWithQuotedFragment match, skipping characters
-        %({{ ,|"' 123 }}) => "{{ 123 }}", # MarkupWithQuotedFragment skipped characters
+        %({{ ,|"' 123 }}) => "{{  123 }}", # MarkupWithQuotedFragment skipped characters
+        "{{,-2}}" => "{{ -2}}", # preserve separators when removing ignored characters
         "{{  12 34  }}" => "{{  12  }}", # no FilterMarkupRegex match, skipping characters
         "{{ -12 34 | abs }}" => "{{ -12 | abs }}", # FilterMarkupRegex skipped characters
         %({{ -12 | '" abs }}) => "{{ -12 |  abs }}", # FilterParser skipped characters