null out else block references when they are destroyed — fixes #509

src/generators/dom/visitors/EachBlock.js

@@ -66,12 +66,16 @@ export default function visitEachBlock ( generator, block, state, node ) {
 					${each_block_else}.mount( ${anchor}.parentNode, ${anchor} );
 				} else if ( ${each_block_else} ) {
 					${each_block_else}.destroy( true );
+					${each_block_else} = null;
 				}
 			` );
 		} else {
 			block.builders.update.addBlock( deindent`
 				if ( ${each_block_value}.length ) {
-					if ( ${each_block_else} ) ${each_block_else}.destroy( true );
+					if ( ${each_block_else} ) {
+						${each_block_else}.destroy( true );
+						${each_block_else} = null;
+					}
 				} else if ( !${each_block_else} ) {
 					${each_block_else} = ${node.else._block.name}( ${params}, ${block.component} );
 					${each_block_else}.mount( ${anchor}.parentNode, ${anchor} );

test/runtime/samples/each-block-dynamic-else-static/_config.js

@@ -23,5 +23,10 @@ export default {
 		assert.htmlEqual( target.innerHTML, `
 			<p>wombat</p>
 		` );
+
+		component.set({ animals: ['dinosaur'] });
+		assert.htmlEqual( target.innerHTML, `
+			<p>dinosaur</p>
+		` );
 	}
 };