Merge remote-tracking branch 'origin/GP-5151-dragonmacher-diff-exception'

Ghidra/Features/ProgramDiff/src/main/java/ghidra/app/plugin/core/diff/CreateDiffTask.java

@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -197,7 +197,7 @@ class CreateDiffTask extends Task {
 			return;
 		}
 
-		if (plugin.getCurrentProgram() == null) {
+		if (plugin.getCurrentProgram() == null || plugin.getSecondProgram() == null) {
 			// the program was closed while this task was running
 			return;
 		}