Avoid creating context for eval if eval is not present

[lahma]

Jint.Benchmark.DromaeoBenchmark

Diff	Method	Prepared	Modern	Toolchain	Mean	Error	Allocated
Old	CoreEval	False	False	Default	4.326 ms	0.0523 ms	335.29 KB
New		False	False	Default	4.055 ms (-6%)	0.0576 ms	335.07 KB (0%)
Old	CoreEval	True	False	Default	4.195 ms	0.0805 ms	320.4 KB
New		True	False	Default	3.250 ms (-23%)	0.1556 ms	319.9 KB (0%)
Old	CoreEval	False	True	Default	5.791 ms	0.0592 ms	334.67 KB
New		False	True	Default	5.713 ms (-1%)	0.0736 ms	334.11 KB (0%)
Old	CoreEval	True	True	Default	4.207 ms	0.1266 ms	320.24 KB
New		True	True	Default	3.107 ms (-26%)	0.0883 ms	319.68 KB (0%)
Old	Cube	False	False	Default	17.182 ms	0.3306 ms	6251.65 KB
New		False	False	Default	15.315 ms (-11%)	0.3507 ms	6108.31 KB (-2%)
Old	Cube	True	False	Default	15.908 ms	0.3078 ms	5910.7 KB
New		True	False	Default	14.575 ms (-8%)	0.1862 ms	5767.14 KB (-2%)
Old	Cube	False	True	Default	15.419 ms	0.3072 ms	6288.92 KB
New		False	True	Default	15.130 ms (-2%)	0.2797 ms	5691.79 KB (-9%)
Old	Cube	True	True	Default	15.910 ms	0.3099 ms	5946.98 KB
New		True	True	Default	15.702 ms (-1%)	0.1648 ms	5349.57 KB (-10%)
Old	ObjectArray	False	False	Default	33.551 ms	0.4204 ms	96269.55 KB
New		False	False	Default	32.569 ms (-3%)	0.5995 ms	96268.71 KB (0%)
Old	ObjectArray	True	False	Default	33.695 ms	0.2893 ms	96222.59 KB
New		True	False	Default	35.738 ms (+6%)	0.5278 ms	96221.35 KB (0%)
Old	ObjectArray	False	True	Default	36.230 ms	0.5786 ms	111437 KB
New		False	True	Default	37.402 ms (+3%)	0.5885 ms	111435.55 KB (0%)
Old	ObjectArray	True	True	Default	40.047 ms	0.7343 ms	111391.03 KB
New		True	True	Default	38.864 ms (-3%)	0.4737 ms	111389.58 KB (0%)
Old	ObjectRegExp	False	False	Default	126.787 ms	2.3528 ms	147813.98 KB
New		False	False	Default	125.974 ms (-1%)	2.4884 ms	152087.7 KB (+3%)
Old	ObjectRegExp	True	False	Default	94.168 ms	1.8010 ms	149495.59 KB
New		True	False	Default	92.926 ms (-1%)	1.7511 ms	150098.73 KB (0%)
Old	ObjectRegExp	False	True	Default	132.146 ms	2.6298 ms	169456.27 KB
New		False	True	Default	133.612 ms (+1%)	2.6541 ms	163936.79 KB (-3%)
Old	ObjectRegExp	True	True	Default	96.971 ms	2.4121 ms	167558.36 KB
New		True	True	Default	96.216 ms (-1%)	1.6825 ms	169688.83 KB (+1%)
Old	ObjectString	False	False	Default	296.005 ms	63.3528 ms	1303449.45 KB
New		False	False	Default	309.999 ms (+5%)	63.1414 ms	1303670.05 KB (0%)
Old	ObjectString	True	False	Default	168.306 ms	3.3354 ms	1303394.14 KB
New		True	False	Default	161.128 ms (-4%)	3.1786 ms	1303379.77 KB (0%)
Old	ObjectString	False	True	Default	164.027 ms	3.2326 ms	1316843.57 KB
New		False	True	Default	162.190 ms (-1%)	3.2269 ms	1317102.48 KB (0%)
Old	ObjectString	True	True	Default	163.129 ms	3.2581 ms	1316720.61 KB
New		True	True	Default	168.724 ms (+3%)	3.3467 ms	1316890.9 KB (0%)
Old	StringBase64	False	False	Default	35.649 ms	0.4043 ms	2397.86 KB
New		False	False	Default	33.227 ms (-7%)	0.4095 ms	2397.23 KB (0%)
Old	StringBase64	True	False	Default	35.956 ms	0.4941 ms	2297.66 KB
New		True	False	Default	39.790 ms (+11%)	0.7608 ms	2296.76 KB (0%)
Old	StringBase64	False	True	Default	40.286 ms	0.4711 ms	12553.82 KB
New		False	True	Default	45.497 ms (+13%)	0.8574 ms	12553.05 KB (0%)
Old	StringBase64	True	True	Default	39.629 ms	0.3965 ms	12452.99 KB
New		True	True	Default	40.311 ms (+2%)	0.3903 ms	12452.23 KB (0%)