fix some bounds checks in FGFCS

[roccoblues]

This looks like copy-n-paste leftovers.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 24.96%. Comparing base (bb4cd5b) to head (e67fc2b).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/models/FGFCS.cpp	0.00%	8 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1191   +/-   ##
=======================================
  Coverage   24.96%   24.96%           
=======================================
  Files         170      170           
  Lines       19283    19283           
=======================================
  Hits         4814     4814           
  Misses      14469    14469           

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[bcoconni]

Thanks for the PR @roccoblues

All these vectors are supposed to have the same size since their size increases simultaneously when FGFCS::AddThrottle is called.

jsbsim/src/models/FGFCS.cpp

Lines 697 to 710 in bb4cd5b

	void FGFCS::AddThrottle(void)
	{
	ThrottleCmd.push_back(0.0);
	ThrottlePos.push_back(0.0);
	MixtureCmd.push_back(0.0); // assume throttle and mixture are coupled
	MixturePos.push_back(0.0);
	PropAdvanceCmd.push_back(0.0); // assume throttle and prop pitch are coupled
	PropAdvance.push_back(0.0);
	PropFeatherCmd.push_back(false);
	PropFeather.push_back(false);
	unsigned int num = (unsigned int)ThrottleCmd.size()-1;
	bindThrottle(num);
	}

However, it indeed improves the code legibility so PR merged.