Reset enemy type in editorclass::reset()

This fixes a bug where if you loaded a level, then started making a new
level in the editor, the enemy types from the previous level would
persist.

While working on VVVVVV: Community Edition and adding a new room
property for enemy speed, I noticed that enemy type was not getting
reset at all. After some testing, I confirmed that this was the case. So
this bug is fixed now.

desktop_version/src/editor.cpp

@@ -314,6 +314,7 @@ void editorclass::reset()
             level[i+(j*maxwidth)].enemyy1=0;
             level[i+(j*maxwidth)].enemyx2=320;
             level[i+(j*maxwidth)].enemyy2=240;
+            level[i+(j*maxwidth)].enemytype=0;
             level[i+(j*maxwidth)].directmode=0;
         }
     }