fix equal condition

Author: andrewseguin

src/lib/table/table-data-source.ts

@@ -123,9 +123,14 @@ export class MatTableDataSource<T> implements DataSource<T> {
 
       let comparatorResult = 0;
       if (valueA && valueB) {
-        comparatorResult = valueA < valueB ? -1 : 1;
+        // Check if one value is greater than the other; if equal, comparatorResult should remain 0.
+        if (valueA < valueB) {
+          comparatorResult = -1;
+        } else if (valueB < valueA) {
+          comparatorResult = 1;
+        }
       } else if (valueA) {
-        comparatorResult  = 1;
+        comparatorResult = 1;
       } else if (valueB) {
         comparatorResult = -1;
       }