Deleting a collection after reordering causes velocity error.

1. Add three new collections
2. Reorder them and save
3. Delete a collection
4. Reorder again
5. Save
6. Delete a collection

Bug
Velocity error

Error number 4001 in 4: Error while parsing velocity page XWiki.DeleteDocument Wrapped Exception: Failed to evaluate content with id Delete Document
Error number 4001 in 4: Error while parsing velocity page XWiki.DeleteDocument
Wrapped Exception: Failed to evaluate content with id Delete Document
com.xpn.xwiki.XWikiException: Error number 4001 in 4: Error while parsing velocity page XWiki.DeleteDocument
Wrapped Exception: Failed to evaluate content with id Delete Document
at com.xpn.xwiki.render.XWikiVelocityRenderer.evaluate(XWikiVelocityRenderer.java:112)
at com.xpn.xwiki.render.XWikiVelocityRenderer.render(XWikiVelocityRenderer.java:87)
at com.xpn.xwiki.render.DefaultXWikiRenderingEngine.renderText(DefaultXWikiRenderingEngine.java:272)
at com.xpn.xwiki.render.DefaultXWikiRenderingEngine.renderText(DefaultXWikiRenderingEngine.java:202)
at com.xpn.xwiki.render.DefaultXWikiRenderingEngine.renderText(DefaultXWikiRenderingEngine.java:170)
at com.xpn.xwiki.render.DefaultXWikiRenderingEngine.renderDocument(DefaultXWikiRenderingEngine.java:159)
at com.xpn.xwiki.doc.XWikiDocument.getRenderedContent(XWikiDocument.java:430)
at com.xpn.xwiki.api.Document.getRenderedContent(Document.java:371)
at sun.reflect.GeneratedMethodAccessor1399.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:295)
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:245)
at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:203)
at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:294)
at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:74)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:318)
at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:107)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:318)
at org.xwiki.velocity.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:178)
at org.xwiki.velocity.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:143)
at com.xpn.xwiki.render.XWikiVelocityRenderer.evaluate(XWikiVelocityRenderer.java:107)
at com.xpn.xwiki.XWiki.parseTemplate(XWiki.java:1648)
at com.xpn.xwiki.XWiki.parseTemplate(XWiki.java:1575)
at com.xpn.xwiki.api.XWiki.parseTemplate(XWiki.java:608)
at sun.reflect.GeneratedMethodAccessor1328.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:295)
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:245)
at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:203)
at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:294)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:318)
at org.apache.velocity.runtime.directive.VelocimacroProxy.render(VelocimacroProxy.java:194)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:170)
at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:74)
at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:88)
at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:74)
at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:88)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:318)