Clean up MATLABCommands on disposal

The DefaultMATLABService will now remove all command variables when its
dispose method is called.

The MATLABBindings were updated to handle null set calls.

Author: hinerm

src/main/java/org/scijava/plugins/scripting/matlab/DefaultMATLABService.java

@@ -93,6 +93,11 @@ public void initialize() {
 		scriptService.addAlias("matrix", MatlabNumericArray.class);
 	}
 
+	@Override
+	public void dispose() {
+		removeCommandVariables();
+	}
+
 	// -- Typed methods --
 
 	@Override
@@ -116,4 +121,16 @@ private synchronized void createCommandVariables() {
 			initializedCommands = true;
 		}
 	}
+
+	/**
+	 * Helper method to remove variables for each {@link MATLABCommands} within
+	 * MATLAB.
+	 */
+	private void removeCommandVariables() {
+		for (final MATLABCommands command : getInstances()) {
+			final String name = command.getInfo().getName();
+
+			makeMATLABVariable(name, null);
+		}
+	}
 }

src/main/java/org/scijava/plugins/scripting/matlab/MATLABBindings.java

@@ -111,11 +111,12 @@ public Object put(final String name, final Object value) {
 		final MatlabProxy proxy = MATLABControlUtils.proxy(opts());
 
 		// Try special MATLAB data types
-		if (MatlabNumericArray.class.isAssignableFrom(value.getClass())) {
+		if (value != null &&
+			MatlabNumericArray.class.isAssignableFrom(value.getClass()))
+		{
 			// Convert the dataset to a MATLAB array and set it as a local variable
 			// within MATLAB.
-			final MatlabTypeConverter converter =
-					new MatlabTypeConverter(proxy);
+			final MatlabTypeConverter converter = new MatlabTypeConverter(proxy);
 			try {
 				converter.setNumericArray(sanitize(name), (MatlabNumericArray) value);
 				return value;