Fix case where the there are no time blocks to determine in a constraint

For FI_Hydro_Reservoir in the EU case, there are no matches in the incoming
flows, so there is nothing constraining the time block. In this case, it uses
1 as time_block_start and num_timesteps and tmie_block_end of the single
block.

Related to #895

docs/src/20-tutorials.md

@@ -127,7 +127,7 @@ variables = compute_variables_indices(dataframes)
 Now we can compute the model.
 
 ```@example manual
-model = create_model(graph, sets, variables, representative_periods, dataframes, years, timeframe, groups, model_parameters)
+model = create_model(connection, graph, sets, variables, representative_periods, dataframes, years, timeframe, groups, model_parameters)
 ```
 
 Finally, we can compute the solution.

src/tmp.jl

@@ -224,7 +224,7 @@ function tmp_create_constraints_indices(connection)
             main.asset,
             main.year,
             main.rep_period,
-            sub.time_block_start,
+            COALESCE(sub.time_block_start, 1) AS time_block_start,
             lead(sub.time_block_start - 1, 1, main.num_timesteps)
                 OVER (PARTITION BY main.asset, main.year, main.rep_period ORDER BY time_block_start)
                 AS time_block_end,
@@ -261,7 +261,7 @@ function tmp_create_constraints_indices(connection)
             main.asset,
             main.year,
             main.rep_period,
-            sub.time_block_start,
+            COALESCE(sub.time_block_start, 1) AS time_block_start,
             lead(sub.time_block_start - 1, 1, main.num_timesteps)
                 OVER (PARTITION BY main.asset, main.year, main.rep_period ORDER BY time_block_start)
                 AS time_block_end,