QmlDesigner: Fix QtDS crash in Property Editor

* Remove dot handling in ExpressionTextField as it was triggering a
  crash of QtDS
* Secure ExpressionTextField with validator to avoid false input

Task-number: QDS-15509
Pick-to: qds/4.7
Change-Id: I3fd9632e8d202a633d6f405ce5523d15088ecb6f
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

share/qtcreator/qmldesigner/propertyEditorQmlSources/imports/HelperWidgets/ComponentSection.qml

@@ -58,6 +58,9 @@ Section {
                     anchors.fill: parent
                     visible: false
                     fixedSize: true
+                    validator: RegularExpressionValidator {
+                        regularExpression: /^[\d\w]*$/
+                    }
 
                     property bool blockEditingFinished: false
 

share/qtcreator/qmldesigner/propertyEditorQmlSources/imports/HelperWidgets/ExpressionTextField.qml

@@ -15,8 +15,6 @@ StudioControls.TextField {
 
     property bool completeOnlyTypes: false
     property bool completionActive: listView.model !== null
-    property bool dotCompletion: false
-    property int dotCursorPos: 0
     property string prefix
     property bool fixedSize: false
     property bool replaceCurrentTextByCompletion: false
@@ -146,14 +144,6 @@ StudioControls.TextField {
 
         switch (event.key) {
 
-        case Qt.Key_Period:
-            textField.dotCursorPos = textField.cursorPosition + 1
-            text = textField.text + "."
-            pos = textField.dotCursorPos
-            explicitComplete = false
-            textField.dotCompletion = true
-            break
-
         case Qt.Key_Right:
             if (!textField.completionActive)
                 return
@@ -209,7 +199,6 @@ StudioControls.TextField {
     //            list.pop()
 
     //        listView.model = list
-    //        textField.dotCompletion = false
 
     //        event.accepted = true
     //    } else {