Tolerate CompletionFailure in JavacTypeBinding

A previous fix has unveiled that some null bindings are sometimes
returned unexpectedly. This is a consequence of CompletionFailure
breaking the key computation.
While it's not clear what is the actual cause and best resolution
for this case, it seems like it's still better to just ignore (and
log) that to forward error and return a null binding.

org.eclipse.jdt.core.javac/src/org/eclipse/jdt/internal/javac/dom/JavacTypeBinding.java

@@ -418,7 +418,7 @@ static void getKey(StringBuilder builder, Type typeToBuild, Name n, boolean isLe
 			try {
 				b2 = typeToBuild.tsym != null && typeToBuild.tsym.type != null && typeToBuild.tsym.type.isParameterized();
 			} catch( CompletionFailure cf1) {
-				throw new BindingKeyException(cf1);
+				ILog.get().error(cf1.getMessage(), cf1);
 			}
 			if ((b1 || b2) && includeParameters) {
 				builder.append('<');