Improve target variable definition

BEfore that a blanc .ccios file was causing issue because template was not defined

lib/ccios/config.rb

@@ -20,10 +20,7 @@ def self.default
   end
 
   def self.default_config_hash
-    {
-        # A blank target by default will use the first one found
-        "variables" => { "target" => "" }
-    }
+    {}
   end
 
   def initialize(config_hash, source_path = nil)

lib/ccios/file_template_definition.rb

@@ -37,7 +37,7 @@ def validate(parser, project, context, template_definition, config)
     raise "Base path \"#{base_path}\" is missing" if base_group.nil?
 
     target_name = merged_variables["target"]
-    if target_name.is_a?(String)
+    if target_name.is_a?(String) || target_name.nil?
       target = parser.target_for(project, target_name)
       raise "Unable to find target \"#{target_name}\"" if target.nil?
     elsif target_name.is_a?(Array)
@@ -77,7 +77,7 @@ def generate(parser, project, context, template_definition, config)
     target_name = merged_variables["target"]
 
     targets = []
-    if target_name.is_a?(String)
+    if target_name.is_a?(String) || target_name.nil?
       targets = [parser.target_for(project, target_name)]
     elsif target_name.is_a?(Array)
       targets = target_name.map { |name| parser.target_for(project, name) }

lib/ccios/pbxproj_parser.rb

@@ -27,7 +27,7 @@ def project_for(path)
   end
 
   def target_for(project, target_name)
-    if target_name.blank?
+    if target_name.blank? || target_name.nil?
       project.targets.find { |t| t.product_type == "com.apple.product-type.application" }
     else
       project.targets.find { |t| t.name == target_name }