Description of problem:
Text-mode anaconda allows to finish partitioning even though no option on the "Partition Scheme Options" screen was selected:


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Partition Scheme Options

[ ] 1) BTRFS

[ ] 2) LVM

[ ] 3) Standard Partition

Select a partition scheme configuration.

  Please make your choice from above ['q' to quit | 'c' to continue]: c
Generating updated storage configuration
Checking storage configuration...
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Installation

 1) [x] Timezone settings                 2) [x] Install Destination
        (US/Eastern timezone)                    (Automatic partitioning selecte
 3) [!] Create user                              d)
        (No user will be created)         4) [!] Set root password
                                                 (Password is not set.)
  Please make your choice from above ['q' to quit | 'c' to continue]:

Version-Release number of selected component (if applicable):
anaconda-19.25-1

How reproducible:
always

Steps to Reproduce:
1. start text mode installation
2. proceed to the screen "Partition Scheme Options"
3. notice that no option is selected
4. select 'c' to continue
  
Actual results:
Anaconda allows to continue even though no option is selected

Expected results:
Anaconda doesn't allow to continue until a valid item is selected, also some item should be preselected by default.