Inspector: Resources tab crashes/resources are not shown

[Nataliya Hristova]

Environment
Provide version numbers for the following components (information can be retrieved by running tns info in your project folder or by inspecting the package.json of the project):

• CLI: 5.1.0-2018-12-05-12706
• iOS Runtime: from PR: Update WebKit from iOS 12.0 tag

Describe the bug
Resources tab crashes immediately when the tab is opened or resources are not shown and when try to choose which resources to be shown - exception is thrown.

To Reproduce

1. Run tns debug ios --inspector
2. Go to Resources tab
3. If it doesn't crash immediately, try to changes the type of resources to be shown

Expected behavior
Resources to be shwon

Sample project

Additional context

TypeError:​ undefined is not an object (evaluating 'this.resources')​ (at FileSystemRepresentationTreeElement.js:​19:​33)​
    onpopulate @ FileSystemRepresentationTreeElement.js:​19:​33
    traverseNextTreeElement @ TreeElement.js:​602:​31
    _updateFilter @ NavigationSidebarPanel.js:​567:​80
    updateFilter @ NavigationSidebarPanel.js:​306:​27
    _scopeBarSelectionDidChange @ ResourceSidebarPanel.js:​513:​26
    dispatch @ Object.js:​170:​30
    dispatchEventToListeners @ Object.js:​177:​17
    _itemSelectionDidChange @ ScopeBar.js:​170:​38
    dispatch @ Object.js:​170:​30
    dispatchEventToListeners @ Object.js:​177:​17
    setSelected @ ScopeBarItem.js:​90:​38
    selected @ ScopeBarItem.js:​79:​25
    _itemSelectionDidChange @ ScopeBar.js:​159:​25
    dispatch @ Object.js:​170:​30
    dispatchEventToListeners @ Object.js:​177:​17
    setSelected @ ScopeBarItem.js:​90:​38
    selected @ ScopeBarItem.js:​79:​25
    selectedScopeBarItem @ MultipleScopeBarItem.js:​137:​39
    selected @ MultipleScopeBarItem.js:​113:​13