Do not crash if IP address could not be determined (#482)

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>

Author: yeban

lib/sequenceserver.rb

@@ -136,9 +136,11 @@ def run
     def on_start
       puts '** SequenceServer is ready.'
       puts "   Go to #{server_url} in your browser and start BLASTing!"
-      puts '   To share your setup, please try one of the following: '
-      puts "     -  http://#{ip_address}:#{config[:port]}"
-      puts "     -  http://#{hostname}:#{config[:port]}" if hostname
+      if ip_address
+        puts '   To share your setup, please try one of the following: '
+        puts "     -  http://#{ip_address}:#{config[:port]}"
+        puts "     -  http://#{hostname}:#{config[:port]}" if hostname
+      end
       puts '   Press CTRL+C to quit.'
       open_in_browser(server_url)
     end
@@ -253,13 +255,14 @@ def server_url
       "http://#{host}:#{config[:port]}"
     end
 
-    # Returns a local ip adress
+    # Returns a local ip adress.
     def ip_address
-      Socket.ip_address_list.find { |ai| ai.ipv4? && !ai.ipv4_loopback? }.ip_address
+      addrinfo = Socket.ip_address_list.find { |ai| ai.ipv4? && !ai.ipv4_loopback? }
+      addrinfo.ip_address if addrinfo
     end
 
-    # Returns machine's hostname based on the local ip;
-    # If hostname cannot be determined then print nothing
+    # Returns machine's hostname based on the local ip. If hostname cannot be
+    # determined returns nil.
     def hostname
       Resolv.getname(ip_address) rescue nil
     end