if there's nothing for the user to select, display nothing.

core/src/main/java/hudson/matrix/MatrixProject.java

@@ -774,18 +774,11 @@ public class MatrixProject extends AbstractProject<MatrixProject,MatrixBuild> im
         else
             executionStrategy = req.bindJSON(esd.get(0).clazz,json.getJSONObject("executionStrategy"));
 
-        try {
-            List<MatrixCheckoutStrategyDescriptor> mrcsd = MatrixCheckoutStrategyDescriptor
-                .all();
-            if (mrcsd.size() > 1)
-                matrixCheckoutStrategy = req.bindJSON(MatrixCheckoutStrategy.class,
-                    json.getJSONObject("matrixCheckoutStrategy"));
-            else
-                matrixCheckoutStrategy = req.bindJSON(mrcsd.get(0).clazz,
-                    json.getJSONObject("matrixCheckoutStrategy"));
-        } catch (Exception exc) {
-            matrixCheckoutStrategy = new DefaultMatrixCheckoutStrategyImpl();
-        }
+        if (json.has("matrixCheckoutStrategy"))
+            matrixCheckoutStrategy = req.bindJSON(MatrixCheckoutStrategy.class,
+                json.getJSONObject("matrixCheckoutStrategy"));
+        else
+            matrixCheckoutStrategy = null;
 
         // parse system axes
         DescribableList<Axis,AxisDescriptor> newAxes = new DescribableList<Axis,AxisDescriptor>(this);

core/src/main/resources/hudson/matrix/MatrixProject/configure-entries.jelly

@@ -58,15 +58,9 @@ THE SOFTWARE.
   <p:config-scm/>
 
   <f:section title="${%Advanced Source Code Management}">
-	<j:choose>
-		<j:when test="${descriptor.matrixRunCheckoutStrategyDescriptors.size() gt 1}">
-			<f:dropdownDescriptorSelector title="${%Matrix Run Checkout Strategy}" field="matrixCheckoutStrategy"/>
-		</j:when>
-		<j:otherwise>
-			<!-- for the default case when there's only one build checkout strategy, render it inline to simplify the UI -->
-			<f:property field="matrixCheckoutStrategy" propertyDescriptor="${descriptor.matrixRunCheckoutStrategyDescriptors.get(0)}"/>
-		</j:otherwise>
-	</j:choose>
+	<j:if test="${descriptor.matrixRunCheckoutStrategyDescriptors.size() gt 1}">
+			<f:dropdownDescriptorSelector title="${%SCM Checkout Strategy}" field="matrixCheckoutStrategy"/>
+  </j:if>
   </f:section>
 
   <p:config-trigger>