make sure the previous modal is hidden before open a new one

src/app/tabs/runTab/settings.js

@@ -273,11 +273,12 @@ class SettingsUI {
       var account = $txOrigin.selectedOptions[0].value
 
       var promptCb = (passphrase) => {
-        modalDialogCustom.promptMulti(signMessageDialog, (message) => {
+        const modal = modalDialogCustom.promptMulti(signMessageDialog, (message) => {
           this.settings.signMessage(message, account, passphrase, (err, msgHash, signedData) => {
             if (err) {
               return addTooltip(err)
             }
+            modal.hide()
             modalDialogCustom.alert(yo`
               <div>
                 <b>hash:</b><br>

src/app/ui/modaldialog.js

@@ -77,7 +77,8 @@ module.exports = (title, content, ok, cancel, focusSelector, opts) => {
   }
 
   function hide () {
-    if (container) container.style.display = 'none'
+    if (!container) return
+    container.style.display = 'none'
     if (container.parentElement) container.parentElement.removeChild(container)
     container = null
   }
@@ -119,7 +120,7 @@ module.exports = (title, content, ok, cancel, focusSelector, opts) => {
       }
     })
   }
-  return { container, okListener, cancelListener }
+  return { container, okListener, cancelListener, hide }
 }
 
 function html (opts) {