Bug 537415 Fix npe in ContentAssistant.show

Signed-off-by: Christian Dietrich <christian.dietrich@itemis.de>
Change-Id: I036cd02358c48e7e94871d4397cfacecbda63e5f
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.text/+/183111
Tested-by: Platform Bot <platform-bot@eclipse.org>
Reviewed-by: Andrey Loskutov <loskutov@gmx.de>
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistant.java b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistant.java
index 3c4a834..21e307e 100644
--- a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistant.java
+++ b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistant.java
@@ -349,6 +349,8 @@
 		}
 
 		protected void showAssist(final int showStyle) {
+			if (fContentAssistSubjectControlAdapter == null)
+				return;
 			final Control control= fContentAssistSubjectControlAdapter.getControl();
 			if (control == null)
 				return;