Gracefully handle perf tool window not being created (#7713)

A workaround for #7691, not accessing the tool window if it wasn't
created due to `isApplicableAsync` being false for the SDK version. Does
it in this listener so if the SDK version changes, the event still can
be handled properly.

Author: parlough

flutter-idea/src/io/flutter/performance/FlutterPerformanceViewFactory.java

@@ -40,8 +40,11 @@ public static void init(@NotNull Project project) {
   private static void initPerfView(@NotNull Project project, FlutterViewMessages.FlutterDebugEvent event) {
     ApplicationManager.getApplication().invokeLater(() -> {
       final FlutterPerformanceView flutterPerfView = project.getService(FlutterPerformanceView.class);
-      ToolWindowManager.getInstance(project).getToolWindow(FlutterPerformanceView.TOOL_WINDOW_ID).setAvailable(true);
-      flutterPerfView.debugActive(event);
+      final ToolWindow window = ToolWindowManager.getInstance(project).getToolWindow(FlutterPerformanceView.TOOL_WINDOW_ID);
+      if (flutterPerfView != null && window != null) {
+        window.setAvailable(true);
+        flutterPerfView.debugActive(event);
+      }
     });
   }