Add doc on fractional share dropdown

Also adds error handling for post-merger avg basis to avoid
DIV0 error when sheet isn't populated.

worksheet/github_hickeng_financial_vmw_avgo_merger_data_Summary.json

@@ -38,7 +38,7 @@
 {"sheet":0,"id":"B40","data":"Cash consideration"},
 {"sheet":0,"id":"B42","data":"=Reference!B31","type":"formula","format":"financial","dataclass":"info","note":"This is what would have been deposited in your individual brokerage account or similar.\nThe Gains and the Fractional sale are the amounts you need to pay tax on."},
 {"sheet":0,"id":"B47","data":"=ESPP!AE5+RSU!AA5","type":"formula","format":"financial","dataclass":"info","note":"This is \"tax\" basis not cost basis and is the sum of:\n1. the money deducted from your paycheck for ESPP purchases (approximately)\n2. the \"tax\" already paid on vesting RSUs, some of which would be through shares that were sold-to-cover, some from additional W2 withholding and makeup tax payments.\n\nRemember that RSUs are considered income when they vest so you pay tax at the point they're released to you."},
-{"sheet":0,"id":"B48","data":"=(B47 - B42)/(F41 + C41)","type":"formula","format":"financial","dataclass":"info","note":"This is a dumb \"(basis-in - cash-received)/shares-out\" calculation, with basis-in still adjusted for the Dell distributions.\n\nIt includes the fraction in shares-out because that's inherently part of it. However the money for the fraction isn't included in the cash-received as the fractional sale doesn't impact basis in other shares.\n\nThis value is provided because it's both an interesting reference and people in countries other than the US have need of this number.\n"},
+{"sheet":0,"id":"B48","data":"=IFERROR((B47 - B42)/(F41 + C41),\"n/a\")","type":"formula","format":"financial","dataclass":"info","note":"This is a dumb \"(basis-in - cash-received)/shares-out\" calculation, with basis-in still adjusted for the Dell distributions.\n\nIt includes the fraction in shares-out because that's inherently part of it. However the money for the fraction isn't included in the cash-received as the fractional sale doesn't impact basis in other shares.\n\nThis value is provided because it's both an interesting reference and people in countries other than the US have need of this number.\n"},
 {"sheet":0,"id":"B51","data":"WARNING"},
 {"sheet":0,"id":"B54","data":"Liability"},
 {"sheet":0,"id":"B55","data":"Actual"},
@@ -141,7 +141,7 @@
 {"sheet":0,"id":"J22","data":"Inputs (Tweaks)"},
 {"sheet":0,"id":"J25","data":"AVGO FMV"},
 {"sheet":0,"id":"J26","data":"Cash/stock ratio","note":"Pro-rata - from Necessary Inputs\n- uses the qty of shares from eTrade transaction log entered into Necessary Inputs to derive a pro-rata ratio\n\nPer-lot - from strategy or manual selection\n- uses a manual slection per-lot for cash/shares preference/ratio. The effective total ratio must still match exactly the overall transaction ratio.\n- This is mostly so I can assess whether it's even worth asking a CPA to look into it.\n- See https://github.com/hickeng/financial/issues/10\n\nPro-rata - from eTrade share qty\n- uses the \"AVGO qty from eTrade\" from OSPS holdings to calculate the effective ratio used per lot\n- from a technical perspective, eTrade seem to have used proration and rounding to find a number of vmw shares for cash vs stock, then a per-lot approach to distribute that across the lots through per-lot ratios. This is inferred from numbers.\n\nPro-rata - from eTrade transaction log\n- uses the \"pure\" value from the eTrade transaction log. The numbers resulting from this do not match any of the concrete numbers we're pinned by, such as cash deposited into accounts."},
-{"sheet":0,"id":"J27","data":"Factional share value"},
+{"sheet":0,"id":"J27","data":"Factional share value","note":"Everyone should use the \"eTrade\" value here - the others are primarily so you can see the  impact of eTrade having sold at a value other than that specified in Form8937.\n\nThere are two concrete values for the fractional share:\n1. the value eTrade sold it at\n2. the value the Form8937 specified it should be sold at\n\nThis dropdown allows for selecting between those to explore impact, or specifying your own value."},
 {"sheet":0,"id":"J28","data":"Post merger sale of AVGO","dataclass":"out_future","note":"Lets you look at the LTG/STG shift based on potential sale dates of the converted AVGO.\n\nIf you set this to last year, then the numbers will be rolled into the tax estimation, so that if you sold in 2023 but post merge this setting is for you.\n\nThis is unlikely to have any effect if using optimized manual lots as the newer lots will all have been assigned to cash."},
 {"sheet":0,"id":"J30","data":"Other Captial Gain (Short)"},
 {"sheet":0,"id":"J31","data":"Other Captial Gain (Long)"},