Ensure 0 does not get formatted to empty string

src/common/string/format_number.ts

@@ -58,7 +58,7 @@ export const formatNumber = (
       ).format(Number(num));
     }
   }
-  return num ? num.toString() : "";
+  return num.toString();
 };
 
 /**

test-mocha/common/string/format_number.ts

@@ -15,6 +15,56 @@ describe("formatNumber", () => {
     );
   });
 
+  it("Test format 'none' (keep dot despite language 'de')", () => {
+    assert.strictEqual(
+      formatNumber(1.23, {
+        language: "de",
+        number_format: NumberFormat.none,
+      }),
+      "1.23"
+    );
+  });
+
+  it("Ensure zero is kept for format 'language'", () => {
+    assert.strictEqual(
+      formatNumber(0, {
+        language: "en",
+        number_format: NumberFormat.language,
+      }),
+      "0"
+    );
+  });
+
+  it("Ensure zero is kept for format 'none'", () => {
+    assert.strictEqual(
+      formatNumber(0, {
+        language: "en",
+        number_format: NumberFormat.none,
+      }),
+      "0"
+    );
+  });
+
+  it("Test empty string input for format 'none'", () => {
+    assert.strictEqual(
+      formatNumber("", {
+        language: "en",
+        number_format: NumberFormat.none,
+      }),
+      ""
+    );
+  });
+
+  it("Test empty string input for format 'language'", () => {
+    assert.strictEqual(
+      formatNumber("", {
+        language: "en",
+        number_format: NumberFormat.language,
+      }),
+      "0"
+    );
+  });
+
   it("Formats number with options", () => {
     assert.strictEqual(
       formatNumber(