No bug - Set assistant status without UI sync

Since Photon RC1 async is safe - see bug #534402

Change-Id: Iea212e9ff98406282fdc77172d21e456f54c3018
Signed-off-by: Dawid Pakuła <zulus@w3des.net>
diff --git a/core/plugins/org.eclipse.dltk.ui/src/org/eclipse/dltk/ui/text/completion/ContentAssistProcessor.java b/core/plugins/org.eclipse.dltk.ui/src/org/eclipse/dltk/ui/text/completion/ContentAssistProcessor.java
index 921f63d..882040e 100644
--- a/core/plugins/org.eclipse.dltk.ui/src/org/eclipse/dltk/ui/text/completion/ContentAssistProcessor.java
+++ b/core/plugins/org.eclipse.dltk.ui/src/org/eclipse/dltk/ui/text/completion/ContentAssistProcessor.java
@@ -419,7 +419,7 @@
 			fAssistant.setStatusMessage(message);
 			fAssistant.setEmptyMessage(emptyMessage);
 		} else {
-			Display.getDefault().syncExec(() -> {
+			Display.getDefault().asyncExec(() -> {
 				fAssistant.setStatusMessage(message);
 				fAssistant.setEmptyMessage(emptyMessage);
 			});
@@ -428,7 +428,9 @@
 		fRepetition++;
 
 		// fAssistant.setShowMessage(fRepetition % 2 != 0);
-
+		if (fCategoryIteration == null) {
+			return fCategories;
+		}
 		return fCategoryIteration.get(iteration);
 	}