erp5_document_scanner: prevent passing empty string as device_id

bt5/erp5_document_scanner/PathTemplateItem/web_page_module/scanner_gadget_document_scanner_js.js

@@ -56,7 +56,9 @@
     return navigator.mediaDevices.getUserMedia({
       video: {
         deviceId: {
-          exact: device_id
+          // Prevent passing empty string as device_id
+          // because it throws OverconstrainedError
+          exact: device_id || undefined
         }
       },
       audio: false

bt5/erp5_document_scanner/PathTemplateItem/web_page_module/scanner_gadget_document_scanner_js.xml

@@ -244,7 +244,7 @@
                   </item>
                   <item>
                       <key> <string>serial</string> </key>
-                      <value> <string>983.2714.63510.3754</string> </value>
+                      <value> <string>983.13237.65489.43861</string> </value>
                   </item>
                   <item>
                       <key> <string>state</string> </key>
@@ -262,7 +262,7 @@
                           </tuple>
                           <state>
                             <tuple>
-                              <float>1586244257.05</float>
+                              <float>1586875663.36</float>
                               <string>UTC</string>
                             </tuple>
                           </state>