fix: singleValueUnserialize is now working more stable

PR viur-framework#1425 introduced a `singleValueUnserialize` implementation that has
no robustness against any other formats.

We still have old StringBone values in the database (`val={'val': '0.5', 'idx': '0.5'}`).
This was never noticed, as there was never an error before.
Now the value can neither be loaded nor ignored, nor does the `getDefaultValue` in except work without parameters.
So no rebuild search index can be made with `refresh()` if the value is not loaded in the first place.

Author: sveneberth

src/viur/core/bones/numeric.py

@@ -83,12 +83,9 @@ def __setattr__(self, key, value):
     def singleValueUnserialize(self, val):
         if val is not None:
             try:
-                if self.precision:
-                    return round(float(val), self.precision)
-
-                return int(val)
-            except ValueError:
-                return self.getDefaultValue()
+                return self._convert_to_numeric(val)
+            except (ValueError, TypeError):
+                return self.getDefaultValue(None)  # FIXME: callable needs the skeleton instance
 
         return val
 
@@ -220,10 +217,12 @@ def _convert_to_numeric(self, value: t.Any) -> int | float:
         """Convert a value to an int or float considering the precision.
 
         If the value is not convertable an exception will be raised."""
+        if isinstance(value, db.Entity | dict) and "val" in value:
+            value = value["val"]  # was a StringBone before
         if isinstance(value, str):
             value = value.replace(",", ".", 1)
         if self.precision:
-            return float(value)
+            return round(float(value), self.precision)
         else:
             # First convert to float then to int to support "42.5" (str)
             return int(float(value))