fix(compiler): keep a custom property declared as 0

src/__tests__/native/variables.test.tsx

@@ -53,6 +53,20 @@ test("combined inline variables", () => {
   });
 });
 
+test("a custom property declared as 0 keeps its value", () => {
+  // Two definitions, so the compiler cannot inline `--my-var`.
+  registerCSS(`
+    .zero { --my-var: 0; }
+    .one { --my-var: 1; }
+    .test { opacity: var(--my-var, 0.5); }
+  `);
+
+  render(<View testID={testID} className="test zero" />);
+
+  const component = screen.getByTestId(testID);
+  expect(component.props.style).toStrictEqual({ opacity: 0 });
+});
+
 test("inherit variables", () => {
   registerCSS(`
     .my-class-1 { width: var(--my-var); }

src/compiler/declarations.ts

@@ -1198,7 +1198,7 @@ export function parseUnparsed(
       property,
       allowAuto,
     );
-    if (!args) return;
+    if (args === undefined) return;
     if (Array.isArray(args) && args.length === 1) {
       return args[0];
     } else if (