Use Util.one helper where applicable

Follow-up to #395 (comment)

Author: viralpraxis

lib/unparser/emitter/dsym.rb

@@ -33,7 +33,7 @@ def emit_str_child(value)
 
       def emit_begin_child(component)
         write('#{')
-        visit(unwrap_single_begin(component)) if component.children.any?
+        visit(Util.one(component.children)) if component.children.any?
         write('}')
       end
     end # DSym

lib/unparser/emitter/flow_modifier.rb

@@ -21,7 +21,7 @@ def dispatch
 
         if children.one? && n_if?(children.first)
           ws
-          emitter(children.first).emit_ternary
+          emitter(Util.one(children)).emit_ternary
         else
           emit_arguments unless children.empty?
         end

lib/unparser/emitter/kwbegin.rb

@@ -12,7 +12,7 @@ def dispatch
         write('begin')
 
         if children.one?
-          emit_body_ensure_rescue(children.first)
+          emit_body_ensure_rescue(Util.one(children))
         else
           indented do
             emit_multiple_body

lib/unparser/emitter/xstr.rb

@@ -64,7 +64,7 @@ def escape_xstr(input)
 
       def emit_begin(component)
         write('#{')
-        visit(unwrap_single_begin(component))
+        visit(Util.one(component.children)) if component.children.any?
         write('}')
       end
     end # XStr

lib/unparser/node_helpers.rb

@@ -84,13 +84,5 @@ def n_range?(node)
       end
       private(name)
     end
-
-    def unwrap_single_begin(node)
-      if n_begin?(node) && node.children.one?
-        node.children.first
-      else
-        node
-      end
-    end
   end # NodeHelpers
 end # Unparser

lib/unparser/writer/array.rb

@@ -24,7 +24,7 @@ def emit_compact # rubocop:disable Metrics/AbcSize
               write(Util.one(child.children).to_s)
             else
               write('#{')
-              emitter(unwrap_single_begin(Util.one(child.children))).write_to_buffer
+              emitter(Util.one(Util.one(child.children).children)).write_to_buffer
               write('}')
             end
           end

test/corpus/literal/literal.rb

@@ -72,3 +72,5 @@
 `  x
 #{foo}
 #`
+`#{}`
+`#G`