fix: always select block after flyout insert (RaspberryPiFoundation#205)

In MakeCode at least, it's possible to open the flyout by tabbing to the
toolbox. In that scenario there is no marker. Because of the early return
keyboard nav flow was broken as the new block wasn't selected.

Author: microbit-matt-hillsdon

src/navigation.ts

@@ -600,20 +600,18 @@ export class Navigation {
     if (!newBlock) {
       return;
     }
-    if (!this.markedNode) {
-      this.warn('No marked node when inserting from flyout.');
-      return;
-    }
-    if (
-      !this.tryToConnectNodes(
-        workspace,
-        this.markedNode,
-        Blockly.ASTNode.createBlockNode(newBlock)!,
-      )
-    ) {
-      this.warn(
-        'Something went wrong while inserting a block from the flyout.',
-      );
+    if (this.markedNode) {
+      if (
+        !this.tryToConnectNodes(
+          workspace,
+          this.markedNode,
+          Blockly.ASTNode.createBlockNode(newBlock)!,
+        )
+      ) {
+        this.warn(
+          'Something went wrong while inserting a block from the flyout.',
+        );
+      }
     }
 
     this.focusWorkspace(workspace);