Fixed bug in Loop Subdivide preview line (cause a crash)

source/blender/src/editmesh.c

@@ -2474,6 +2474,7 @@ void loop(int mode)
 							}
 						}
 						else{	/* if it's a triangular face, set the remaining vertex as the cutcurve coordinate */
+							if(a!=2){
 								if(evl->v1->f & 16){
 									cen[a][0]= evl->v1->co[0];
 									cen[a][1]= evl->v1->co[1];
@@ -2493,6 +2494,7 @@ void loop(int mode)
 									evl->v3->f &= ~16;
 								}
 							}
+						}
 							
 						
 						glVertex3fv(cen[0]);