Handle if asdf which java errors (#272)

This can happen if the java plugin is install but no version has been
installed yet.

Author: convergedtarkus

set-java-home.bash

@@ -6,8 +6,7 @@ function _asdf_java_absolute_dir_path {
 
 function _asdf_java_update_java_home() {
   local java_path
-  java_path="$(asdf which java)"
-  if [[ -n "${java_path}" ]]; then
+  if java_path=$(asdf which java 2>&1) && [[ -n $java_path ]]; then
     export JAVA_HOME
     JAVA_HOME="$(dirname "$(_asdf_java_absolute_dir_path "${java_path}")")"
     export JDK_HOME=${JAVA_HOME}

set-java-home.zsh

@@ -1,7 +1,6 @@
 asdf_update_java_home() {
   local java_path
-  java_path="$(asdf which java)"
-  if [[ -n "${java_path}" ]]; then
+  if java_path=$(asdf which java 2>&1) && [[ -n $java_path ]]; then
     export JAVA_HOME
     JAVA_HOME="$(dirname "$(dirname "${java_path:A}")")"
     export JDK_HOME=${JAVA_HOME}