Theme: Support null for color_scheme_tint

Fixes #370

Author: FichteFoll

Package/Sublime Text Theme/Sublime Text Theme.sublime-syntax

@@ -27,12 +27,15 @@ variables:
       | monospace_background_color
       | shadow_color
       | viewport_color
-      | color_scheme_tint(?:_2)?
       | color\d+
       | link_color # from Sublime Merge
       | (?:accent_)?tint_modifier
       | (?:left|right|top|bottom)_shadow
     )
+  tint_key: |-
+    (?x:
+        color_scheme_tint(?:_2)?
+    )
   color_adjuster_key: |-
     (?x:
         background_modifier # 4095
@@ -254,6 +257,14 @@ contexts:
         2: keyword.other.rule.sublime-theme
         3: punctuation.definition.string.end.json
       set: [expect-color-value, expect-colon]
+    # tint values
+    - match: (")({{tint_key}})(")
+      scope: meta.mapping.key.json meta.rule-key.color.sublime-theme string.quoted.double.json
+      captures:
+        1: punctuation.definition.string.begin.json
+        2: keyword.other.rule.sublime-theme
+        3: punctuation.definition.string.end.json
+      set: [expect-tint-value, expect-colon]
     # color adjuster values
     - match: (")({{color_adjuster_key}})(")
       scope: meta.mapping.key.json meta.rule-key.color-adjuster.sublime-theme string.quoted.double.json

Package/Sublime Text Theme/syntax_test_newstyletheme.json

@@ -123,14 +123,18 @@
 // <- invalid.illegal.expected-comma.inside-mapping.json
 //          ^^^^^^^^^^^^^^^^^^^^^^ meta.rule-key.color.sublime-theme
 //                                         ^^^ support.function.var.css
-            "layer1.tint": null,
-//                         ^^^^ meta.mapping.value.json constant.language.null.json
             "layer2.tint": "color(var(--bluish) min-contrast(rgb(235, 237, 239) 2.5))",
 //                          ^^^^^ support.function.color.css
 //                                ^^^ support.function.var.css
 //                                              ^^^^^^^^^^^^ support.function.min-contrast.css
 //                                                           ^^^ support.function.color.css
 //                                                                              ^^^ constant.numeric
+        },
+        { // tints (like colors but support `null`)
+            "color_scheme_tint": null,
+//                               ^^^^ meta.mapping.value.json constant.language.null.json
+            "layer1.tint": null,
+//                         ^^^^ meta.mapping.value.json constant.language.null.json
         },
         { // color adjusters
             "background_modifier": "blend(white 97.5%)"