removed extra lines from the compilation of trailing `then` with `if`/`switch`

lib/nodes.js

@@ -1651,7 +1651,7 @@
       return this;
     };
     Switch.prototype.compileNode = function(o) {
-      var _i, _j, _len, _len2, _ref2, _ref3, _ref4, _ref5, block, code, cond, conditions, expr, i, idt1, idt2;
+      var _i, _j, _len, _len2, _ref2, _ref3, _ref4, _ref5, block, body, code, cond, conditions, expr, i, idt1, idt2;
       idt1 = this.idt(1);
       idt2 = o.indent = this.idt(2);
       code = this.tab + ("switch (" + (((_ref2 = this.subject) != null ? _ref2.compile(o, LEVEL_PAREN) : undefined) || false) + ") {\n");
@@ -1665,7 +1665,9 @@
           }
           code += idt1 + ("case " + (cond.compile(o, LEVEL_PAREN)) + ":\n");
         }
-        code += block.compile(o, LEVEL_TOP) + '\n';
+        if (body = block.compile(o, LEVEL_TOP)) {
+          code += body + '\n';
+        }
         if (i === this.cases.length - 1 && !this.otherwise) {
           break;
         }
@@ -1744,7 +1746,10 @@
       cond = this.condition.compile(o, LEVEL_PAREN);
       o.indent = this.idt(1);
       body = this.ensureExpressions(this.body).compile(o);
-      ifPart = "if (" + cond + ") {\n" + body + "\n" + this.tab + "}";
+      if (body) {
+        body = "\n" + body + "\n" + this.tab;
+      }
+      ifPart = "if (" + cond + ") {" + body + "}";
       if (!child) {
         ifPart = this.tab + ifPart;
       }

src/nodes.coffee

@@ -1367,7 +1367,7 @@ exports.Switch = class Switch extends Base
       for cond in flatten [conditions]
         cond  = cond.invert() unless @subject
         code += idt1 + "case #{ cond.compile o, LEVEL_PAREN }:\n"
-      code += block.compile(o, LEVEL_TOP) + '\n'
+      code += body + '\n' if body = block.compile o, LEVEL_TOP
       break if i is @cases.length - 1 and not @otherwise
       for expr in block.expressions by -1 when expr not instanceof Comment
         code += idt2 + 'break;\n' unless expr instanceof Return
@@ -1432,7 +1432,8 @@ exports.If = class If extends Base
     cond     = @condition.compile o, LEVEL_PAREN
     o.indent = @idt 1
     body     = @ensureExpressions(@body).compile o
-    ifPart   = "if (#{cond}) {\n#{body}\n#{@tab}}"
+    body     = "\n#{body}\n#{@tab}" if body
+    ifPart   = "if (#{cond}) {#{body}}"
     ifPart   = @tab + ifPart unless child
     return ifPart unless @elseBody
     ifPart + ' else ' + if @isChain