fix(datepicker): fix daterangepicker crash on empty value

Author: IlyaSurmay

demo/src/app/components/+datepicker/demos/bs-popup/date-picker-popup.html

@@ -15,7 +15,7 @@
 <br>
 
 <pre>{{bsRangeValue}}</pre>
-<pre>{{ bsRangeValue[0] | date:'yMd'}} - {{ bsRangeValue[1] | date:'yMd'}}</pre>
+<pre *ngIf="bsRangeValue">{{ bsRangeValue[0] | date:'yMd'}} - {{ bsRangeValue[1] | date:'yMd'}}</pre>
 <input #drp="bsDaterangepicker" bsDaterangepicker [(bsValue)]="bsRangeValue">
 <input bsDaterangepicker [(ngModel)]="bsRangeValue">
 <input [(ngModel)]="bsRangeValue">

package.json

@@ -10,7 +10,7 @@
     "demo.serve": "run-s build link demo.docs demo.build docs.archive lite-server",
     "demo.serve-fast": "run-s build link demo.docs demo.build-fast docs.archive lite-server",
     "demo.gh-pages": "run-s build demo.docs demo.build docs.archive demo.deploy",
-    "demo.build": "ng build -prod --aot --build-optimizer --preserve-symlinks -nc",
+    "demo.build": "ng build -prod --aot --preserve-symlinks -nc",
     "demo.build-fast": "ng build",
     "demo.deploy": "gh-pages -d gh-pages",
     "demo-beta-deploy": "gh-pages -d gh-pages -r git@github.com:valorkin/ngx-bootstrap.git -b gh-pages",

src/datepicker/bs-daterangepicker-input.directive.ts

@@ -37,13 +37,13 @@ export class BsDaterangepickerInputDirective
           v[0],
           this._picker._config.rangeInputFormat,
           this._picker._config.locale
-        );
+        ) || '';
         const end = formatDate(
           v[1],
           this._picker._config.rangeInputFormat,
           this._picker._config.locale
-        );
-        range = start + this._picker._config.rangeSeparator + end;
+        ) || '';
+        range = (start && end) ? start + this._picker._config.rangeSeparator + end : '';
       }
       this._renderer.setProperty(this._elRef.nativeElement, 'value', range);
       this._onChange(v);
@@ -58,6 +58,7 @@ export class BsDaterangepickerInputDirective
   writeValue(value: Date[] | string) {
     if (!value) {
       this._picker.bsValue = null;
+      return;
     }
 
     const _locale = getLocale(this._picker._config.locale);