scripting: Throw properly in TraceScriptingModule

Replace throwing of NullPointerException with IllegalArgumentException.

Change-Id: I1ff24dfca26c3c642eef85f3bdda9577be0dec3d
Signed-off-by: Marco Miller <marco.miller@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/c/tracecompass.incubator/org.eclipse.tracecompass.incubator/+/193692
Tested-by: Trace Compass Bot <tracecompass-bot@eclipse.org>
Tested-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>

scripting/org.eclipse.tracecompass.incubator.scripting.core/src/org/eclipse/tracecompass/incubator/scripting/core/trace/TraceScriptingModule.java

@@ -187,7 +187,7 @@ private static ITmfTrace openAndInitializeTrace(IFile file, String location, Str
     @WrapToScript
     public ScriptEventsIterator getEventIterator(@Nullable ITmfTrace trace) {
         if (trace == null) {
-            throw new NullPointerException("Trace should not be null"); //$NON-NLS-1$
+            throw new IllegalArgumentException("Trace should not be null"); //$NON-NLS-1$
         }
 
         ScriptEventRequest scriptEventRequest = new ScriptEventRequest();