Fix edge case for falsy values

Author: amomchilov

Diff for: lib/debug/server_cdp.rb

@@ -1114,7 +1114,9 @@ def process_cdp args
       when :properties
         oid = args.shift
 
-        if obj = @obj_map[oid]
+        if @obj_map.key?(oid)
+          obj = @obj_map[oid]
+
           members = if Array === obj
             VariableInspector.new.indexed_members_of(obj, start: 0, count: obj.size)
           else

Diff for: lib/debug/server_dap.rb

@@ -869,8 +869,10 @@ def process_dap args
         event! :protocol_result, :scope, req, variables: vars, tid: self.id
       when :variable
         vid = args.shift
-        obj = @var_map[vid]
-        if obj
+
+        if @var_map.key?(vid)
+          obj = @var_map[vid]
+
           members = case req.dig('arguments', 'filter')
           when 'indexed'
             VariableInspector.new.indexed_members_of(

Diff for: test/protocol/step_back_raw_dap_test.rb

@@ -883,7 +883,7 @@ def test_step_back_works_correctly
                   namedVariables: /\d+/,
                   indexedVariables: 0,
                   expensive: false,
-                  variablesReference: 11
+                  variablesReference: 12
                 },
                 {
                   name: "Global variables",
@@ -917,15 +917,15 @@ def test_step_back_works_correctly
                   name: "%self",
                   value: "Foo",
                   type: "Module",
-                  variablesReference: 12,
+                  variablesReference: 13,
                   indexedVariables: 0,
                   namedVariables: /\d+/
                 },
                 {
                   name: "bar",
                   value: "nil",
                   type: "NilClass",
-                  variablesReference: 13,
+                  variablesReference: 14,
                   indexedVariables: 0,
                   namedVariables: /\d+/
                 }