fix NullPointerException in Theme Selector (resolves #476)

app/src/processing/app/contrib/ManagerFrame.java

@@ -139,10 +139,14 @@ public class ManagerFrame {
 
 
   protected void updateTheme() {
-    Color bgColor = Theme.getColor("manager.tab.background");
-    frame.getContentPane().setBackground(bgColor);
+    // don't update if the Frame doesn't actually exist yet
+    // https://github.com/processing/processing4/issues/476
+    if (frame != null) {
+      Color bgColor = Theme.getColor("manager.tab.background");
+      frame.getContentPane().setBackground(bgColor);
 
-    tabs.updateTheme();
+      tabs.updateTheme();
+    }
   }
 
 

todo.txt

@@ -9,6 +9,8 @@ X   no longer pass a blank sketch file name from startup script
 X   also remove unused readlink
 X   support multiple files passed on command line
 X only show setWritable() failure in recent.txt when it is a problem
+X NullPointerException when changing the theme
+X   https://github.com/processing/processing4/issues/476
 
 design
 X set minimum size for scroll bar thumb