Issue #456: Crash: broken formula + clicking on the f(x) symbol (dismine/valentina)

New issue 456: Crash: broken formula + clicking on the f(x) symbol https://bitbucket.org/valentinateam/valentina/issues/456/crash-broken-formula-clicking-on-the-f-x

Robin Lilian:

When I enter a formula like “2+”, “2-” or “2*” and then click on the f(x) symbol to use a variable, the program crashes, telling me: “Parser Error: Unexpected end of expression on position [15 for -, 12 for *, 2 for +]”. For the record I did this in the little extra window called “Tool Settings” (or similar, I’m translating here). Valentina Version 0.4.2, Windows 8.1 32-bit.