feat: improve errors when entity is unavailable

[makspll]

Summary

Many places in BMS use Entity::from_raw(0) as an invalid entity, because that index is not naturally assigned to any entity in Bevy.

When an entity is not available in a callback, i.e. on_script_loaded people often try to interact with the entity global, this PR makes it so that using those entities, will throw a more meaningful error and point people to this fact.

Also fixes minor newline issue in docs

[github-actions]

Bencher Report

Branch	feat/better-entity-errors
Testbed	linux-gha

Click to view all benchmark results

Benchmark	Latency	Benchmark Result nanoseconds (ns) (Result Δ%)	Upper Boundary nanoseconds (ns) (Limit %)
component/access Lua	📈 view plot 🚷 view threshold	3,414.80 ns (-30.38%) Baseline: 4,904.69 ns	6,382.88 ns (53.50%)
component/access Rhai	📈 view plot 🚷 view threshold	5,707.20 ns (-15.63%) Baseline: 6,764.87 ns	8,025.00 ns (71.12%)
component/get Lua	📈 view plot 🚷 view threshold	2,040.10 ns (-29.20%) Baseline: 2,881.61 ns	3,588.65 ns (56.85%)
component/get Rhai	📈 view plot 🚷 view threshold	4,443.00 ns (-10.22%) Baseline: 4,948.98 ns	6,020.58 ns (73.80%)
conversions/Mut::from	📈 view plot 🚷 view threshold	80.03 ns (-40.86%) Baseline: 135.32 ns	247.94 ns (32.28%)
conversions/Ref::from	📈 view plot 🚷 view threshold	79.12 ns (-40.62%) Baseline: 133.25 ns	245.65 ns (32.21%)
conversions/ScriptValue::List	📈 view plot 🚷 view threshold	260.66 ns (-58.55%) Baseline: 628.82 ns	1,114.00 ns (23.40%)
conversions/ScriptValue::Map	📈 view plot 🚷 view threshold	1,233.20 ns (-25.71%) Baseline: 1,660.03 ns	2,219.37 ns (55.57%)
conversions/ScriptValue::Reference::from_into	📈 view plot 🚷 view threshold	25.01 ns (-38.64%) Baseline: 40.76 ns	58.69 ns (42.61%)
conversions/Val::from_into	📈 view plot 🚷 view threshold	212.72 ns (-37.21%) Baseline: 338.78 ns	465.06 ns (45.74%)
function/call 4 args Lua	📈 view plot 🚷 view threshold	1,659.40 ns (-20.85%) Baseline: 2,096.44 ns	2,515.75 ns (65.96%)
function/call 4 args Rhai	📈 view plot 🚷 view threshold	1,450.40 ns (-20.19%) Baseline: 1,817.36 ns	2,213.77 ns (65.52%)
function/call Lua	📈 view plot 🚷 view threshold	227.54 ns (-18.73%) Baseline: 279.96 ns	336.75 ns (67.57%)
function/call Rhai	📈 view plot 🚷 view threshold	448.51 ns (-15.35%) Baseline: 529.87 ns	664.33 ns (67.51%)
math/vec mat ops Lua	📈 view plot 🚷 view threshold	5,983.50 ns (-23.03%) Baseline: 7,774.27 ns	9,307.29 ns (64.29%)
math/vec mat ops Rhai	📈 view plot 🚷 view threshold	5,785.80 ns (-22.34%) Baseline: 7,450.54 ns	8,647.21 ns (66.91%)
query/10 entities Lua	📈 view plot 🚷 view threshold	17,951.00 ns (-27.33%) Baseline: 24,702.12 ns	30,757.33 ns (58.36%)
query/10 entities Rhai	📈 view plot 🚷 view threshold	19,860.00 ns (-18.48%) Baseline: 24,362.53 ns	28,815.47 ns (68.92%)
query/100 entities Lua	📈 view plot 🚷 view threshold	38,669.00 ns (-22.60%) Baseline: 49,962.59 ns	61,449.55 ns (62.93%)
query/100 entities Rhai	📈 view plot 🚷 view threshold	29,698.00 ns (-24.16%) Baseline: 39,159.35 ns	48,132.14 ns (61.70%)
query/1000 entities Lua	📈 view plot 🚷 view threshold	252,460.00 ns (-19.29%) Baseline: 312,780.59 ns	385,749.00 ns (65.45%)
query/1000 entities Rhai	📈 view plot 🚷 view threshold	159,140.00 ns (-27.84%) Baseline: 220,545.59 ns	300,234.48 ns (53.01%)
reflection/10 Lua	📈 view plot 🚷 view threshold	5,559.10 ns (-15.29%) Baseline: 6,562.77 ns	7,568.86 ns (73.45%)
reflection/10 Rhai	📈 view plot 🚷 view threshold	14,866.00 ns (-9.61%) Baseline: 16,446.68 ns	18,023.75 ns (82.48%)
reflection/100 Lua	📈 view plot 🚷 view threshold	47,372.00 ns (-11.58%) Baseline: 53,578.06 ns	60,456.54 ns (78.36%)
reflection/100 Rhai	📈 view plot 🚷 view threshold	721,470.00 ns (-2.28%) Baseline: 738,277.94 ns	871,654.45 ns (82.77%)
resource/access Lua	📈 view plot 🚷 view threshold	3,009.80 ns (-30.25%) Baseline: 4,315.15 ns	5,549.45 ns (54.24%)
resource/access Rhai	📈 view plot 🚷 view threshold	5,018.50 ns (-17.00%) Baseline: 6,046.35 ns	7,452.39 ns (67.34%)
resource/get Lua	📈 view plot 🚷 view threshold	1,685.00 ns (-29.79%) Baseline: 2,399.81 ns	3,034.45 ns (55.53%)
resource/get Rhai	📈 view plot 🚷 view threshold	3,733.10 ns (-13.05%) Baseline: 4,293.55 ns	5,336.37 ns (69.96%)

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