fix stray else in compress with conditionals=false

closes #1449

lib/compress.js

@@ -1840,6 +1840,8 @@ merge(Compressor.prototype, {
     });
 
     OPT(AST_If, function(self, compressor){
+        if (is_empty(self.alternative)) self.alternative = null;
+
         if (!compressor.option("conditionals")) return self;
         // if condition can be statically determined, warn and drop
         // one of the blocks.  note, statically determined implies
@@ -1868,7 +1870,6 @@ merge(Compressor.prototype, {
                 }
             }
         }
-        if (is_empty(self.alternative)) self.alternative = null;
         var negated = self.condition.negate(compressor);
         var self_condition_length = self.condition.print_to_string().length;
         var negated_length = negated.print_to_string().length;