Add defensive code for handler & converter plugins

None of the following should throw an exception (checked or otherwise):

* Instantiating a plugin.
* Calling Typed.supports(...) on a TypedPlugin.
* Calling getInputType() or getOutputType() on a Converter.

Any exceptions thrown in those scenarios indicate a malfunction.
The relevant service layers now log such exceptions and continue.

Author: ctrueden

src/main/java/org/scijava/convert/AbstractConvertService.java

@@ -150,7 +150,13 @@ public Collection<Class<?>> getCompatibleOutputClasses(final Class<?> source) {
 		final Set<Class<?>> compatibleClasses = new HashSet<>();
 
 		for (final Converter<?, ?> converter : getInstances()) {
-			addIfMatches(source, converter.getInputType(), converter.getOutputType(), compatibleClasses);
+			try {
+				addIfMatches(source, converter.getInputType(), converter.getOutputType(), compatibleClasses);
+			}
+			catch (final Throwable t) {
+				log().error("Malfunctioning converter plugin: " + //
+					converter.getClass().getName(), t);
+			}
 		}
 
 		return compatibleClasses;

src/main/java/org/scijava/plugin/HandlerService.java

@@ -57,7 +57,12 @@ public interface HandlerService<DT, PT extends HandlerPlugin<DT>> extends
 	 */
 	default PT getHandler(final DT data) {
 		for (final PT handler : getInstances()) {
-			if (handler.supports(data)) return handler;
+			try {
+				if (handler.supports(data)) return handler;
+			}
+			catch (final Throwable t) {
+				log().error("Malfunctioning plugin: " + handler.getClass().getName(), t);
+			}
 		}
 		return null;
 	}

src/main/java/org/scijava/plugin/TypedService.java

@@ -68,8 +68,13 @@ public interface TypedService<DT, PT extends TypedPlugin<DT>> extends
 	 */
 	default PT find(final DT data) {
 		for (final PluginInfo<PT> plugin : getPlugins()) {
-			final PT instance = pluginService().createInstance(plugin);
-			if (instance != null && instance.supports(data)) return instance;
+			try {
+				final PT instance = pluginService().createInstance(plugin);
+				if (instance != null && instance.supports(data)) return instance;
+			}
+			catch (final Throwable t) {
+				log().error("Malfunctioning plugin: " + plugin.getClassName(), t);
+			}
 		}
 		return null;
 	}