gh-146092: Fix error handling in _BINARY_OP_ADD_UNICODE opcode (#146117)

Fix also error handling in _BINARY_OP_ADD_FLOAT,
_BINARY_OP_SUBTRACT_FLOAT and _BINARY_OP_MULTIPLY_FLOAT opcodes.
PyStackRef_FromPyObjectSteal() must not be called with a NULL
pointer.
4 files changed