Fixed regression in toggling subpatch gop redrect

* It is supposed to toggle on and off depending on whether the subpatch has scalars only in it. It does this by also intelligently accounting for temporary text objects that are created and need to be filled by the scalar name before they are converted into a scalar class.

* There is one condition the original implementation failed to account for: creating a new text_object in an empty canvas which erroneously still resulted in the assumption that the subpatch consisted of only scalars.

* This patch fixes this special case.

* To test: create an empty subpatch and enable GOP, inside the subpatch create an empty object which will erase GOP until you make that object something concrete (e.g. print). With the patch, the GOP redrect will never dissappear (and it shouldn't).
8 jobs for gop-redrect-n-scalars-regression in 232 minutes and 22 seconds (queued for 57 minutes and 40 seconds)
latest
Status Name Job ID Coverage
  Test
passed debian_stretch_x86_64_deb #22402
debian stretch x86_64

00:40:18

passed osx_10.11_x86_64_dmg #22404
osx v10.11 dmg

00:23:43

passed osx_10.8_x86_64_dmg #22405
osx v10.8 dmg

00:21:29

failed raspbian_stretch_armv7l_deb #22407
raspbian arm stretch

passed ubuntu_16.04_x86_64_deb #22403
ubuntu v16.04 x86_64

00:35:00

passed windows_i386_innosetup #22422
windows i386

01:51:51

passed windows_i386_innosetup #22421
i386 windows

02:05:44

failed windows_i386_innosetup #22406
windows i386

00:00:48

 
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failed
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