A bug when scale by image

[uestchang]

兄弟，缩放之后会出问题啊，裁剪框飞出图片外面去了；而且缩放没有限制最小值，导致裁剪框会被压成一条线。有时间的话，能帮忙修复吗，这个库要是完善起来，简直就是福音了。

[uestchang]

缩放过程中旋转会直接卡死。

2019-06-17 12:43:30.692335+0800 LyEditImageView[4328:1938937] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unable to parse constraint format:
Cannot tell if this - is a minus sign or an accidental extra bar in the connection. Use parentheses around negative numbers.
H:|--0.000000-[cropView]-0.000000-|
^'
*** First throw call stack:
(0x18536ed8c 0x1845285ec 0x185ed3d64 0x185d1917c 0x185d189f4 0x185d185e4 0x1001a4dc8 0x1001a97d8 0x1001a694c 0x1001a6980 0x18f0dd64c 0x18f1fe870 0x18f0e3700 0x18f2191a8 0x18f1609e0 0x18f155890 0x18f1541d0 0x18f935d1c 0x18f9382c8 0x18f931368 0x185317404 0x185316c2c 0x18531479c 0x185234da8 0x18721a020 0x18f254758 0x1001b81a8 0x184cc5fc0)
libc++abi.dylib: terminating with uncaught exception of type NSException