Check rows.Err() in the remaining Next() loops (#27)

Incident list, the three stats breakdowns and the user list could return a
truncated result as if complete when the scan failed partway.

internal/api/incidents.go

@@ -100,6 +100,10 @@ func handleListIncidents(db *sql.DB) http.HandlerFunc {
 			}
 			incidents = append(incidents, i)
 		}
+		if err := rows.Err(); err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
 		respond(w, http.StatusOK, incidents)
 	}
 }