Treat nil and blank values as different

Before:
When searching for "", it found records with a nil value.

After:
It will find nil values when searching for nil
It will not find nil values when searching for ''

lib/active_hash/condition.rb

@@ -39,6 +39,6 @@ def matches_value?(value, comparison)
   end
 
   def normalize(value)
-    value.respond_to?(:to_s) ? value.to_s : value
+    value.respond_to?(:to_s) ? value&.to_s : value
   end
 end

spec/active_hash/base_spec.rb

@@ -465,7 +465,8 @@ class Region < ActiveHash::Base
       Country.data = [
         {:id => 1, :name => "US", :language => 'English'},
         {:id => 2, :name => "Canada", :language => 'English'},
-        {:id => 3, :name => "Mexico", :language => 'Spanish'}
+        {:id => 3, :name => "Mexico", :language => 'Spanish'},
+        {:id => 5, :name => "Any", :language => nil}
       ]
     end
 
@@ -524,6 +525,14 @@ class Region < ActiveHash::Base
     it "returns nil when passed a wrong id" do
       expect(Country.find_by(:id => 4)).to be_nil
     end
+
+    it "finds record by nil value" do
+      expect(Country.find_by(:language => nil).id).to eq(5)
+    end
+
+    it "doesn't finds nil records when searching for ''" do
+      expect(Country.find_by(:language => '')).to be_nil
+    end
   end
 
   describe ".find_by!" do