made functions more rezilient

src/lib/utils/functions.ts

@@ -1,12 +1,18 @@
-import { tap } from 'rxjs/operators';
+import {tap} from 'rxjs/operators';
 
 export function capitalize(value: string): string {
+    if (!value) {
+        return "";
+    }
     return value.charAt(0).toUpperCase() + value.slice(1);
 }
 
 export function humanize(value: string, lowercase = true): string {
-    const words = (lowercase ? value.toLowerCase() : value).split(/[ \-_]+/);
+    if (!value) {
+        return "";
+    }
 
+    const words = (lowercase ? value.toLowerCase() : value).split(/[ \-_]+/);
     return words.map(capitalize).join(' ');
 }