resilience to a blank space in the magic cell of top left

src/viralhostrange/test_data/space_top_left.xlsx.json

+{
+  "C1": {
+    "r1": "0",
+    "r2": "0",
+    "r3": "0"
+  },
+  "C2": {
+    "r1": "1",
+    "r2": "1",
+    "r3": "2"
+  },
+  "C3": {
+    "r1": "0",
+    "r2": "2",
+    "r3": "0"
+  },
+  "C4": {
+    "r1": "2",
+    "r2": "0",
+    "r3": "0"
+  }
+}
\ No newline at end of file

src/viralhostrange/viralhostrangedb/business_process.py

@@ -163,6 +163,7 @@ def parse_file(file, importation_observer: ImportationObserver = None):
         virus = None
         virus_identifier = None
         for id_col, cell in enumerate(sub_row):
+            cell = cell.strip()
             if header is None or not has_seen_data and id_col == 1 and sub_row[0] == "":
                 if cell is not "" and not cell.startswith("Unnamed: "):
                     header = row