fix: allow blank input

Author: scttcper

src/format-input.ts

@@ -105,6 +105,9 @@ const matchers = {
  */
 export function stringInputToObject(color: string): any {
   color = color.trim().toLowerCase();
+  if (color.length === 0) {
+    return false;
+  }
   let named = false;
   if (names[color]) {
     color = names[color];

src/index.ts

@@ -49,9 +49,6 @@ export class TinyColor {
     }
     this.originalInput = color;
     const rgb = inputToRGB(color);
-    if (!color) {
-      return;
-    }
     this.originalInput = color;
     this.r = rgb.r;
     this.g = rgb.g;

test/index.spec.ts

@@ -227,6 +227,10 @@ describe('TinyColor', () => {
     invalidColor = new TinyColor({ h: 'invalid', s: 'invalid', v: 'invalid' } as any);
     expect(invalidColor.toHexString()).toBe('#000000');
     expect(invalidColor.isValid).toBe(false);
+
+    invalidColor = new TinyColor();
+    expect(invalidColor.toHexString()).toBe('#000000');
+    expect(invalidColor.isValid).toBe(false);
   });
   it('Named colors', () => {
     expect(new TinyColor('aliceblue').toHex()).toBe('f0f8ff');