[Task] Fix the issue with chemical formula input

This task is for the second stage of implementation after we submit the first PR as specified in issue #15 (closed). Before starting putting in new implementations, we need to make sure that our starting point for the second stage of implementation is the final version that is merged into neutron/addie master branch. When submitting our first PR, there may be some changes needed to address comments from reviewers and we want to make sure the starting point of the second stage implementation does contain all those changes.

• Reproduce the issue.

  • Clicking on the ... button inside Chemical Formula box to bring up the chemical formula input window.

  • Manual input whatever chemical formula will give error at the bottom bar of the window and the program refuses to continue to save the formula.

  • However, clicking on those elements shown in periodic table to input chemical formula will not bring up any error.

• Locate the issue in code.

  There may be some flag in the code whereby it will be automatically set to True when inputting by clicking on the periodic table. Such a flag should also be set to True if user does manually input suitable chemical formula. Here regular expression may be needed to check the suitability of the manually input chemical formula. Such an implementation should already exist in the code and the error should be just something to do with this part of codes.

• Solve the issue.

• Meeting for discussion if needed.

• Issue solved and mark the task as Complete.