Fix for (this.value || "").split is not a function

If value is not a String, we got an error. 
To fix issue, first convert value to string, then split it.

lib/components/form-input.vue

@@ -28,7 +28,7 @@
         mixins: [formMixin],
         computed: {
             rowsCount() {
-                return (this.value || '').split('\n').length;
+                return (this.value.toString() || '').split('\n').length;
             }
         },
         methods: {