fix(s1): avoid negative zero

Author: missinglink

s1/angle.ts

@@ -46,7 +46,7 @@ export const radians = (a: Angle): number => a
 /**
  * Returns the angle in degrees.
  */
-export const degrees = (a: Angle): number => a / DEGREE
+export const degrees = (a: Angle): number => a / DEGREE || 0
 
 /**
  * Returns the value rounded to nearest as an int32.

s1/angle_test.ts

@@ -19,6 +19,10 @@ describe('s1.angle', () => {
     // Check negative angles.
     equal(angle.degrees((-Math.PI / 2) * RADIAN), -90, '(-π/2 * Radian).Degrees() was %v, want -90')
     equal(angle.radians(-45 * DEGREE), -Math.PI / 4, '(-45 * Degree).Radians() was %v, want -π/4')
+
+    // zero(s)
+    equal(angle.degrees(0), 0, 'positive zero')
+    equal(angle.degrees(-0), 0, 'negative zero')
   })
 
   test('E5/E6/E7 representation', (t) => {