The ornamental design for an inflatablebag, as shown and described.
FIG. 1 is a front elevational view of an inflatable bag showing my new design;
FIG. 2 is an enlarged fragmentary front elevational view illustrating a portion of the inflatable bag in the oval region in FIG. 1;
FIG. 3 is a front perspective view thereof;
FIG. 4 is a fragmentary front perspective view thereof taken from another angle; and,
FIG. 5 is a fragmentary rear perspective view thereof.
The evenly dashed broken lines depict portions of an inflatable bag in which the design is embodied that form no part of the claimed design. The dot-dashed broken lines are for defining the bounds of the claimed design only and form no part of the claimed design.