java, make: avoid errors in nounset mode on Ubuntu 14 and 16

completions/java

@@ -88,10 +88,12 @@ _java_classes()
         fi
     done
 
-    # remove class extension
-    COMPREPLY=(${COMPREPLY[@]%.class})
-    # convert path syntax to package syntax
-    COMPREPLY=(${COMPREPLY[@]//\//.})
+    if ((${#COMPREPLY[@]} != 0)); then
+        # remove class extension
+        COMPREPLY=(${COMPREPLY[@]%.class})
+        # convert path syntax to package syntax
+        COMPREPLY=(${COMPREPLY[@]//\//.})
+    fi
 }
 
 # available packages completion
@@ -111,12 +113,14 @@ _java_packages()
                 command sed -e 's|^'$i'/||'))
         fi
     done
-    # keep only packages
-    COMPREPLY=($(tr " " "\n" <<<"${COMPREPLY[@]}" | command grep "/$"))
-    # remove packages extension
-    COMPREPLY=(${COMPREPLY[@]%/})
-    # convert path syntax to package syntax
-    cur="${COMPREPLY[*]//\//.}"
+    if ((${#COMPREPLY[@]} != 0)); then
+        # keep only packages
+        COMPREPLY=($(tr " " "\n" <<<"${COMPREPLY[@]}" | command grep "/$"))
+        # remove packages extension
+        COMPREPLY=(${COMPREPLY[@]%/})
+        # convert path syntax to package syntax
+        cur="${COMPREPLY[*]//\//.}"
+    fi
 }
 
 # java completion

completions/make

@@ -154,7 +154,7 @@ _make()
         local IFS=$' \t\n' script=$(_make_target_extract_script $mode "$cur")
         COMPREPLY=($(LC_ALL=C \
             $1 -npq __BASH_MAKE_COMPLETION__=1 \
-            "${makef[@]}" "${makef_dir[@]}" .DEFAULT 2>/dev/null |
+            ${makef+"${makef[@]}"} "${makef_dir[@]}" .DEFAULT 2>/dev/null |
             command sed -ne "$script"))
 
         if [[ $mode != -d ]]; then