Fix wrong empty string formatting (#15949)

As title, solves this kind of issues
https://twentyfortwenty.twenty.com/object/workflowRun/d6aca50e-68ba-4715-8835-ea22bd44fb88

Solves null currencyDisplay when null currencyCode and null amountMicros

### Before
<img width="147" height="81" alt="image"
src="https://github.com/user-attachments/assets/d250d65e-b984-43f4-ad67-1397a684cf6a"
/>

 ### After
 
<img width="128" height="74" alt="image"
src="https://github.com/user-attachments/assets/4f9c9d80-f8bb-495a-9be0-ecfb984ded81"
/>

packages/twenty-shared/src/utils/variable-resolver.test.ts

@@ -10,12 +10,31 @@ describe('resolveInput', () => {
       theme: 'dark',
       notifications: true,
     },
+    specialValues: {
+      nullValue: null,
+      undefinedValue: undefined,
+      emptyString: '',
+      zero: 0,
+      booleanFalse: false,
+      booleanTrue: true,
+    },
   };
 
   it('should return null for null input', () => {
     expect(resolveInput(null, context)).toBeNull();
   });
 
+  it('should support special values', () => {
+    expect(resolveInput('{{specialValues.nullValue}}', context)).toBeNull();
+    expect(
+      resolveInput('{{specialValues.undefinedValue}}', context),
+    ).toBeUndefined();
+    expect(resolveInput('{{specialValues.emptyString}}', context)).toBe('');
+    expect(resolveInput('{{specialValues.zero}}', context)).toBe(0);
+    expect(resolveInput('{{specialValues.booleanFalse}}', context)).toBe(false);
+    expect(resolveInput('{{specialValues.booleanTrue}}', context)).toBe(true);
+  });
+
   it('should return undefined for undefined input', () => {
     expect(resolveInput(undefined, context)).toBeUndefined();
   });