- handled a possible situation in App.load_defaults() method

- fixed some issues in FlatCAMDB that may appear in certain scenarios

README.md

@@ -1,18 +1,19 @@
 FlatCAM BETA (c) 2019 - by Marius Stanciu
 Based on FlatCAM: 
 2D Computer-Aided PCB Manufacturing by (c) 2014-2016 Juan Pablo Caram
-=================================================
+=====================================================================
 
 FlatCAM is a program for preparing CNC jobs for making PCBs on a CNC router.
 Among other things, it can take a Gerber file generated by your favorite PCB
 CAD program, and create G-Code for Isolation routing.
 
-=================================================
+=====================================================================
 
------------- Installation instructions ----------
+-------------------------- Installation instructions ----------------
 
 Works with Python version 3.5 or greater and PyQt5.
 More on the YouTube channel: https://www.youtube.com/playlist?list=PLVvP2SYRpx-AQgNlfoxw93tXUXon7G94_
+
 You can contact me on my email address found in the app in:
 Menu -> Help -> About FlatCAM -> Programmers -> Marius Stanciu
 
@@ -20,7 +21,7 @@ Menu -> Help -> About FlatCAM -> Programmers -> Marius Stanciu
 - Download sources from: https://bitbucket.org/jpcgt/flatcam/downloads/
 - Unzip them on a HDD location that your user has permissions for.
 
-1. Windows
+1.Windows
 - download the provided installer (for your OS flavor 64bit or 32bit) from:
 https://bitbucket.org/jpcgt/flatcam/downloads/
 - execute the installer and install the program. It is recommended to install as a Local User.
@@ -33,7 +34,10 @@ Use one of the versions (64bit or 32it) that are compatible with your OS.
 To save space use one of the versions that have the smaller size (they offer 2 versions: one with size of few hundred MB and one smaller with size of few tens of MB)
 
 - add Python folder and Python\Scripts folder to your Windows Path (https://docs.microsoft.com/en-us/previous-versions/office/developer/sharepoint-2010/ee537574(v%3Doffice.14))
-- verify that the pip package can be run by opening Command Prompt(Admin) and running the command: pip -V
+- verify that the pip package can be run by opening Command Prompt(Admin) and running the command:
+```
+pip -V
+```
 
 - look in the requirements.txt file (found in the sources folder) and install all the dependencies using the pip package. 
 The required wheels can be downloaded either from:
@@ -42,23 +46,40 @@ or
 https://pypi.org/
  
 You can download all the required wheels files into a folder (e.g D:\my_folder) and install them from Command Prompt like this:
+
+```
 cd D:\my_folder
+```
+
 and for each wheel file (*.whl) run:
+```
 D:\my_folder\> pip install --upgrade package_from_requirements.whl
+```
 
 Run FlatCAM beta from the installation folder (e.g D:\FlatCAM_beta) in the Command Prompt with the following command:
 cd D:\FlatCAM_beta
 python FlatCAM.py
 
-2. Linux
+2.Linux
 - make sure that Python 3.8 is installed on your OS and that the command: python3 -V confirm it
-- verify that the pip package is installed for your Python installation (e.g 3.8) by running the command pip3 -V. 
+- verify that the pip package is installed for your Python installation (e.g 3.8) by running the command:
+```
+pip3 -V
+``` 
+
 If it is not installed, install it. In Ubuntu-like OS's it is done like this: 
+```
 sudo apt-get install python3-pip 
+```
 or:
+```
 sudo apt-get install python3.8-pip
+```
 - verify that the file setup_ubuntu.sh has Linux line-endings (LF) and that it is executable (chmod +x setup_ubuntu.sh)
-- run the file setup_ubuntu.sh and install all the dependencies with the command: ./setup_ubuntu.sh
+- run the file setup_ubuntu.sh and install all the dependencies with the command:
+```
+./setup_ubuntu.sh
+```
 - if the previous command is successful and has no errors, run FlatCAM with the command: python3 FlatCAM.py
 
 - Alternatively you can install it on Ubuntu with:
@@ -73,7 +94,8 @@ make install
 sudo make install
 ```
 
-3. MacOS
+3.MacOS
+
 Instructions from here: https://gist.github.com/natevw/3e6fc929aff358b38c0a#gistcomment-3111878
 
 - create a folder to hold the sources somewhere on your HDD: