[TD] fix arrow end None for dimensions

This was not merged from my PR to PR #3153

- also uniform the combobox appearance in the preferences

src/Mod/TechDraw/Gui/DlgPrefsTechDraw3.ui

@@ -140,9 +140,6 @@
           <property name="currentIndex">
            <number>-1</number>
           </property>
-          <property name="maxVisibleItems">
-           <number>5</number>
-          </property>
           <property name="prefEntry" stdset="0">
            <cstring>ArrowStyle</cstring>
           </property>
@@ -215,7 +212,7 @@
          </widget>
         </item>
         <item row="5" column="2">
-         <widget class="Gui::PrefUnitSpinBox" name="plsb_FontSize">
+         <widget class="Gui::PrefUnitSpinBox" name="plsb_FontSize" native="true">
           <property name="sizePolicy">
            <sizepolicy hsizetype="Preferred" vsizetype="Preferred">
             <horstretch>0</horstretch>
@@ -225,7 +222,7 @@
           <property name="toolTip">
            <string>Dimension font size</string>
           </property>
-          <property name="value">
+          <property name="value" stdset="0">
            <double>4.000000000000000</double>
           </property>
           <property name="prefEntry" stdset="0">
@@ -237,7 +234,7 @@
          </widget>
         </item>
         <item row="8" column="2">
-         <widget class="Gui::PrefUnitSpinBox" name="plsb_ArrowSize">
+         <widget class="Gui::PrefUnitSpinBox" name="plsb_ArrowSize" native="true">
           <property name="sizePolicy">
            <sizepolicy hsizetype="Preferred" vsizetype="Preferred">
             <horstretch>0</horstretch>
@@ -247,7 +244,7 @@
           <property name="toolTip">
            <string>Dimension arrowhead size</string>
           </property>
-          <property name="value">
+          <property name="value" stdset="0">
            <double>5.000000000000000</double>
           </property>
           <property name="prefEntry" stdset="0">

src/Mod/TechDraw/Gui/QGIViewDimension.cpp

@@ -1198,8 +1198,12 @@ void QGIViewDimension::drawArrows(int count, const Base::Vector2d positions[], d
         arrow->setSize(QGIArrow::getPrefArrowSize());
         arrow->setFlipped(flipped);
 
-        arrow->draw();
-        arrow->show();
+        if (QGIArrow::getPrefArrowStyle() != 0) { // if not "None"
+            arrow->draw();
+            arrow->show();
+        }
+        else
+            arrow->hide();
     }
 }