ValueFormats: check for inf (#19376)

packages/grafana-ui/src/utils/valueFormats/valueFormats.test.ts

 import { toFixed, getValueFormat } from './valueFormats';
 
 describe('valueFormats', () => {
+  describe('toFixed with edge cases', () => {
+    it('should handle non number input gracefully', () => {
+      expect(toFixed(NaN)).toBe('NaN');
+      expect(toFixed(Number.NEGATIVE_INFINITY)).toBe('-Inf');
+      expect(toFixed(Number.POSITIVE_INFINITY)).toBe('Inf');
+    });
+  });
+
   describe('toFixed and negative decimals', () => {
     it('should treat as zero decimals', () => {
       const str = toFixed(186.123, -2);

packages/grafana-ui/src/utils/valueFormats/valueFormats.ts

@@ -33,6 +33,12 @@ export function toFixed(value: number, decimals?: DecimalCount): string {
   if (value === null) {
     return '';
   }
+  if (value === Number.NEGATIVE_INFINITY) {
+    return '-Inf';
+  }
+  if (value === Number.POSITIVE_INFINITY) {
+    return 'Inf';
+  }
 
   const factor = decimals ? Math.pow(10, Math.max(0, decimals)) : 1;
   const formatted = String(Math.round(value * factor) / factor);