Should be fixed in r39337-39340.
Note that I have made a couple of incompatible changes:
1) Extracted equation text-related code in a separate unit. Besides slight shortening of TAFuncSeries, which is becoming too large, this code can now be unit-tested, since TAFitUtils unit does not depend on graphics.
2) ExecFit is now called lazily instead of previous eager implementation. This gives both minor optimization and more consistent code, but may require user code to manually call ExecFit in some cases. Also, FValidFitParams boolean is replaced by State enumeration to represent "unknown" validation state.