Non-numerical inputs (excluding constants) only throw errors when they are beside a digit in a mathematical operation when they should throw errors anytime they are typed

[castelliam]

Typing a letter alone (such as a,b,c,etc.) - other than "e" - in a mathematical operation will not produce a result/do anything. But, when we place a number beside that letter (say 4c, 8h+5, etc.), this results in a parsing error. We think that there should always be an error message that appears alerting the user this is not an acceptable input.

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Version Details: Using VirtualBox (firmware), Fedora Release 20 Heisenbug (Build), Image(Sugar 0.103.2, Ubuntu 64-bit v.14.04.1)