Fixes #1932: Better VersionChecker exception handling

ModVersionFetcher will now return a MissingVersion in case of an exception
instead of letting it propagate upwards.

Also added a generic try/catch to the VersionChecker itself, just in case
any unchecked exception might be triggered inside the thread and at least
not logged correctly.

src/main/java/appeng/services/version/BaseVersion.java

@@ -1,7 +1,30 @@
+/*
+ * This file is part of Applied Energistics 2.
+ * Copyright (c) 2013 - 2015, AlgorithmX2, All rights reserved.
+ *
+ * Applied Energistics 2 is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Applied Energistics 2 is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Applied Energistics 2.  If not, see <http://www.gnu.org/licenses/lgpl>.
+ */
 
 package appeng.services.version;
 
 
+import javax.annotation.Nonnegative;
+import javax.annotation.Nonnull;
+
+import com.google.common.base.Preconditions;
+
+
 /**
  * Base version of {@link Version}.
  *
@@ -9,8 +32,11 @@ package appeng.services.version;
  */
 public abstract class BaseVersion implements Version
 {
+	@Nonnegative
 	private final int revision;
+	@Nonnull
 	private final Channel channel;
+	@Nonnegative
 	private final int build;
 
 	/**
@@ -20,10 +46,11 @@ public abstract class BaseVersion implements Version
 	 *
 	 * @throws AssertionError if assertion are enabled and revision or build are not natural numbers
 	 */
-	public BaseVersion( final int revision, final Channel channel, final int build )
+	public BaseVersion( @Nonnegative final int revision, @Nonnull final Channel channel, @Nonnegative final int build )
 	{
-		assert revision >= 0;
-		assert build >= 0;
+		Preconditions.checkArgument( revision >= 0 );
+		Preconditions.checkNotNull( channel );
+		Preconditions.checkArgument( build >= 0 );
 
 		this.revision = revision;
 		this.channel = channel;
@@ -58,7 +85,7 @@ public abstract class BaseVersion implements Version
 	public final int hashCode()
 	{
 		int result = this.revision;
-		result = 31 * result + ( this.channel != null ? this.channel.hashCode() : 0 );
+		result = 31 * result + this.channel.hashCode();
 		result = 31 * result + this.build;
 		return result;
 	}