Fix completer size on plasma6

resources/qml/Completer.qml

@@ -112,7 +112,7 @@ Control {
             ListView.delayRemove: true
             color: model.index == popup.currentIndex ? palette.highlight : palette.base
             height: (chooser.child?.implicitHeight ?? 0) + 2 * popup.rowMargin
-            implicitWidth: fullWidth ? ListView.view.width : chooser.child.implicitWidth + 4
+            implicitWidth: popup.fullWidth ? ListView.view.width : chooser.child.implicitWidth + 4
 
             MouseArea {
                 id: mouseArea

resources/qml/ForwardCompleter.qml

@@ -38,7 +38,7 @@ Popup {
         roomTextInput.forceActiveFocus();
     }
 
-    Column {
+    contentItem: Column {
         id: forwardColumn
 
         spacing: 5

resources/qml/MessageInput.qml

@@ -340,10 +340,9 @@ Rectangle {
                         }
                     }
 
-                    Completer {
+                    contentItem: Completer {
                         id: completer
 
-                        anchors.fill: parent
                         rowMargin: 2
                         rowSpacing: 0
                     }

resources/qml/QuickSwitcher.qml

@@ -32,8 +32,7 @@ Popup {
         roomTextInput.forceActiveFocus();
     }
 
-    Column {
-        anchors.fill: parent
+    contentItem: Column {
         spacing: 1
 
         MatrixTextField {