Ignore empty strings registered as sensitive

Fixes #9462

lib/vagrant/util/credential_scrubber.rb

@@ -30,7 +30,7 @@ module Vagrant
       # @param [String] string
       # @return [String]
       def self.desensitize(string)
-        string = string.dup
+        string = string.to_s.dup
         sensitive_strings.each do |remove|
           string.gsub!(remove, REPLACEMENT_TEXT)
         end
@@ -39,7 +39,10 @@ module Vagrant
 
       # Register a sensitive string to be scrubbed
       def self.sensitive(string)
-        sensitive_strings.push(string).uniq!
+        string = string.to_s.dup
+        if string.length > 0
+          sensitive_strings.push(string).uniq!
+        end
         nil
       end
 

test/unit/vagrant/util/credential_scrubber_test.rb

@@ -34,6 +34,16 @@ describe Vagrant::Util::CredentialScrubber do
       subject.sensitive("value")
       expect(subject.sensitive_strings.count("value")).to eq(1)
     end
+
+    it "should not add an empty string" do
+      subject.sensitive("")
+      expect(subject.sensitive_strings).to be_empty
+    end
+
+    it "should type cast input to string" do
+      subject.sensitive(2)
+      expect(subject.sensitive_strings.first).to eq("2")
+    end
   end
 
   describe ".unsensitive" do