Bug 575643 - omit "null" in Status without exception

It is getting logged in
org.eclipse.tea.core.TaskExecutionContext#execute

Change-Id: Id89b49167cc0a2b11885376dae36d71b43c3c1ee
Signed-off-by: Joerg Kubitz <jkubitz-eclipse@gmx.de>
Reviewed-on: https://git.eclipse.org/r/c/equinox/rt.equinox.bundles/+/184448
Tested-by: Lars Vogel <Lars.Vogel@vogella.com>
Tested-by: Equinox Bot <equinox-bot@eclipse.org>
Reviewed-by: Lars Vogel <Lars.Vogel@vogella.com>
diff --git a/bundles/org.eclipse.equinox.common/src/org/eclipse/core/runtime/Status.java b/bundles/org.eclipse.equinox.common/src/org/eclipse/core/runtime/Status.java
index e7b3351..0393476 100644
--- a/bundles/org.eclipse.equinox.common/src/org/eclipse/core/runtime/Status.java
+++ b/bundles/org.eclipse.equinox.common/src/org/eclipse/core/runtime/Status.java
@@ -461,8 +461,10 @@
 		buf.append(code);
 		buf.append(' ');
 		buf.append(message);
-		buf.append(' ');
-		buf.append(exception);
+		if (exception != null) {
+			buf.append(' ');
+			buf.append(exception);
+		}
 		return buf.toString();
 	}
 }