Fix reading/writing float variant-based props

When variant support was added for props, the validation checks in the
float related functions weren't updated to allow them.

Tested with the plugin from the forum thread with a spawned
`math_counter`.

Fixes #1501

core/smn_entities.cpp

@@ -1132,7 +1132,7 @@ static cell_t SetEntDataString(IPluginContext *pContext, const cell_t *params)
 		auto *pVariant = (variant_t *)((intptr_t)pEntity + offset); \
 		if (pVariant->fieldType != type) \
 		{ \
-			return pContext->ThrowNativeError("Variant value for %s is not %s (%d)", \
+			return pContext->ThrowNativeError("Variant value for %s is not a %s (%d)", \
 				prop, \
 				typeName, \
 				pVariant->fieldType); \
@@ -1572,13 +1572,15 @@ static cell_t GetEntPropFloat(IPluginContext *pContext, const cell_t *params)
 			FIND_PROP_DATA(td);
 
 			if (td->fieldType != FIELD_FLOAT
-				&& td->fieldType != FIELD_TIME)
+				&& td->fieldType != FIELD_TIME
+				&& (td->fieldType != FIELD_CUSTOM || (td->flags & FTYPEDESC_OUTPUT) != FTYPEDESC_OUTPUT))
 			{
-				return pContext->ThrowNativeError("Data field %s is not a float (%d != [%d,%d])", 
+				return pContext->ThrowNativeError("Data field %s is not a float (%d != [%d,%d,%d])", 
 					prop,
 					td->fieldType,
 					FIELD_FLOAT,
-					FIELD_TIME);
+					FIELD_TIME,
+					FIELD_CUSTOM);
 			}
 
 			CHECK_SET_PROP_DATA_OFFSET();
@@ -1633,13 +1635,15 @@ static cell_t SetEntPropFloat(IPluginContext *pContext, const cell_t *params)
 			FIND_PROP_DATA(td);
 
 			if (td->fieldType != FIELD_FLOAT
-				&& td->fieldType != FIELD_TIME)
+				&& td->fieldType != FIELD_TIME
+				&& (td->fieldType != FIELD_CUSTOM || (td->flags & FTYPEDESC_OUTPUT) != FTYPEDESC_OUTPUT))
 			{
-				return pContext->ThrowNativeError("Data field %s is not a float (%d != [%d,%d])", 
+				return pContext->ThrowNativeError("Data field %s is not a float (%d != [%d,%d,%d])", 
 					prop,
 					td->fieldType,
 					FIELD_FLOAT,
-					FIELD_TIME);
+					FIELD_TIME,
+					FIELD_CUSTOM);
 			}
 
 			CHECK_SET_PROP_DATA_OFFSET();